Free Online Utilities

Convert between Solar and Lunar (Chinese) dates, with Gan-Zhi year, zodiac animal and solar terms — powered by lunar-javascript, 100% in your browser.

🧮

Workday Calculator

Count working days between two dates, excluding weekends and custom holidays — 100% in your browser.

⏰

Stopwatch

Centisecond-precision stopwatch with multi-lap timing, fastest / slowest highlight and keyboard shortcuts.

⏰

Countdown Timer

Track days / hours / minutes / seconds to an event; save a list of events locally.

📅

Almanac (万年历 / 老黄历)

A month calendar with Chinese lunar dates, solar terms, Gan-Zhi and daily Yi / Ji.

📅

Date Calculator

Add or subtract days, weeks, months or years from a date, or calculate the interval between two dates.

Encode / Decode

🔐

Base64 Encode / Decode

Encode text to Base64 or decode Base64 back to text, fully in your browser.

🔐

URL Encode / Decode

Percent-encode or decode URLs and query parameters in the browser.

🔐

Hash / MD5 / SHA Calculator

Compute MD5, SHA-1/256/384/512, CRC32 and HMAC signatures locally.

📐

Number Base Converter

Convert between binary, octal, decimal and hexadecimal instantly.

🔐

Unicode / ASCII / Hex Converter

Convert text to Unicode code points or hex escapes, and decode back.

🔐

File / Image to Base64

Convert any file or image to a Base64 data URL, or decode Base64 back to a file.

🔐

Morse Code Encode / Decode

Convert text to and from International Morse Code, with Unicode escape for non-Latin characters.

🔐

Morse Code Audio

Play Morse code as Web Audio tones. Adjustable pitch (Hz) and speed (WPM), live symbol highlight, WAV export.

🔐

Download Link Converter

Convert any URL to / from Thunder, Xuanfeng (qqdl) and FlashGet protocols — plus magnet / ed2k detection.

🔐

Base32 / Base58 / Base62 Encoder

Two-way conversion between text and Base32 (RFC 4648), Base58 (Bitcoin) and Base62 — pure front-end, BigInt-based big-integer base conversion.

🔤

Character Code / ASCII Table

Complete ASCII (0-127) and Extended ASCII (128-255) tables plus a Unicode codepoint ↔ character converter.

Generators

🔐

UUID / GUID Generator

Generate RFC-4122 v4 UUIDs using a cryptographically secure random source.

📱

QR Code Generator

Turn text or a URL into a downloadable QR code image.

🎨

Color Picker & Palette

Pick colors and convert between HEX, RGB and HSL with a palette generator.

⚙️

Lottie Animation Previewer

Preview Lottie JSON animations in your browser with play, pause, loop and speed control.

📝

Random Password Generator

Generate strong, secure passwords with custom length and character sets — 100% in your browser.

📱

Barcode Generator

Generate barcodes (CODE128, EAN13, UPC, CODE39, ITF14 and more) and download as PNG — 100% client-side.

⚙️

Lorem Ipsum Generator

Generate placeholder text in paragraphs or words — 100% in your browser.

🎲

Random Picker / Wheel

Enter options and spin the wheel to pick a random winner — 100% in your browser.

⚙️

Font Awesome Icon Search

Search, preview and copy Font Awesome 6 icons as HTML — 100% in your browser.

⚙️

Color Contrast Checker (WCAG)

Compute the WCAG contrast ratio between foreground and background colors and check AA/AAA compliance — 100% in your browser.

⚙️

Daily Trending

Today's hot searches from Baidu (China) or Google Trends (global) — auto-selected by network, links open the source.

🎨

Color Scheme Generator

Generate complementary, analogous, triadic, split-complementary, tetradic and monochrome palettes from a base color — HSL math, no library.

⚙️

Coupon / Activation Code Generator

Batch-generate random coupon or activation codes with crypto-strong, unbiased randomness — 100% client-side.

⚙️

Online Sticky Notes

Quick, private, local-only sticky notes — add, color, search, drag-to-reorder and pin. Saved in your browser only.

⚙️

Shield Badge Generator

Create shields.io-style badges for your README — color, style, logo. Live preview + URL + markdown + SVG.

🎲

Lottery Wheel — Random Picker

Import a name list and spin the wheel to draw random winners. Supports multi-winner draws without repeats — 100% in your browser.

Text Processing

🔎

Regular Expression Tester

Test JavaScript regular expressions with live match highlighting.

🀄

Variable Name Converter

Convert identifiers between camelCase, snake_case, kebab-case and PascalCase.

🔤

Text Diff Checker

Compare two text blocks side by side and highlight the differences.

🔤

Text Processing Tool

Remove duplicate lines, trim whitespace, sort, convert case and more text operations.

🤖

Email Validator

Validate email addresses in bulk, split valid and invalid ones, and copy the results — 100% in your browser.

🔤

URL Slug Generator

Turn any title into a clean, URL-friendly slug — lowercase, ASCII, hyphen-separated — 100% in your browser.

📝

Number to Words

Convert a number into English words and Chinese characters — 100% in your browser.

🔤

Translator

Translate text across 20+ languages with auto source detection — Google Translate via CORS proxy, no API key.

🔤

ASCII Art Text

Render English text as large characters built from symbols — a compact built-in block font, no library.

🔤

ASCII Table Generator

Turn CSV / TSV data into a Markdown table, an ASCII-bordered table or an HTML table with alignment control.

🔤

Text Dedup

Remove duplicate lines from a list — keep first occurrence or sort, with case / trim / blank-line options.

📝

Keyword Density Analyzer

Count word / n-gram frequency and density for SEO copy review — Chinese 2-4 char n-grams plus English tokens with stopword filtering.

🔤

English Abbreviations

180+ common English abbreviations across IT, business, medicine, chat and international organizations.

🔤

Text Utilities

Reverse, shuffle, strip blank lines, number lines, slice columns, vertical layout and full/half-width conversion — all in your browser.

🧾

CSV Tools — CSV / JSON / TSV / Table

Convert CSV ↔ JSON ↔ TSV and preview / edit as a table. Custom delimiter, quote handling, header toggle.

🔤

Text Statistics

Live counts of characters, words, sentences, paragraphs and lines plus reading time and top keywords.

🔤

LaTeX Formula Editor

Type LaTeX math and see it rendered live by KaTeX. Insert common templates with one click.

Chinese Tools

🀄

Simplified ↔ Traditional Chinese Converter

Convert between Simplified and Traditional Chinese with Taiwan / Hong Kong word-choice variants — powered by opencc-js, 100% in your browser.

📝

Forbidden Words Checker

Scan Chinese marketing copy against ~160 built-in restricted terms — China ad-law superlatives, e-commerce and short-video bans. 100% local.

🀄

Chinese to Pinyin Converter

Convert Chinese characters to Mandarin pinyin with tone marks, numbers, or initials only — polyphones auto-resolved by pinyin-pro.

🀄

Chinese Character Decomposer

Look up a character's radical (偏旁部首), stroke count and structure (上下 / 左右 / 包围 / 独体) — built-in data for ~450 common characters.

🀄

Homophone Pun Finder

Type a word or character to find built-in Chinese internet homophone puns (谐音梗) — 耗子尾汁, 雨女无瓜, 鸭梨山大 and ~40 more.

🀄

Acrostic Poem Generator

Generate Chinese acrostic poems (藏头诗) from a word — random assembly from a built-in corpus, entertainment-grade only.

🔤

Character & Word Counter

Count characters, words, lines, sentences, paragraphs and reading time — live, in your browser.

🃏

Chinese ID Card Validator

Validate an 18-digit (or 15-digit legacy) Chinese ID, check the ISO 7064 MOD-11-2 check digit and extract birth date, gender and region — in your browser.

🀄

Baby Name Generator

Generate Chinese baby name suggestions from a built-in library of 200+ characters tagged with meanings and Wu-Xing elements.

🌐

Typing Speed Test

Measure your WPM and accuracy with live feedback; pick Chinese or English passages.

🀄

Chinese Surnames (百家姓)

Browse and search the classic Hundred Family Surnames — single and compound, with Pinyin and rank.

🀄

Idiom Dictionary & Chain

Chinese idiom (成语) look-up, word-chain game and structure filters — all in your browser.

🀄

Xiehouyu (歇后语)

Chinese two-part allegorical sayings — search, browse and get a random one.

🀄

Special Symbols

Copy emoji, punctuation, math, box-drawing, currency, Greek, arrows and more — one click.

🀄

Synonyms & Antonyms

Look up synonyms and antonyms for common Chinese words.

🀄

Chinese Riddles (字谜灯谜)

Guess character, idiom and thing riddles — search, filter and random.

🀄

Classical Poems & 飞花令

Search Tang / Song poems and play Feihualing — every verse containing a given character.

🀄

Chinese Classics (国学启蒙)

Full text of San Zi Jing, Qian Zi Wen, Bai Jia Xing and Di Zi Gui — read and copy.

🀄

Famous Quotes (名言名句)

Classic Chinese and Western quotes — search by author or text, plus a random one.

🀄

Couplets (对联 / 春联)

Spring Festival couplets, scenic-hall couplets and trade couplets — search, filter, browse.

🀄

Area Code / ZIP / Plate

Look up a Chinese city by name, area code, ZIP code or license-plate prefix.

📅

Chinese Zodiac (十二生肖)

Enter a birth year to get the zodiac animal, personality, best matches and fortune.

🀄

Zodiac Signs (星座)

Enter a birthday (month / day) to get the Western zodiac sign, traits, element and best matches.

🀄

Dream Interpretation (周公解梦)

Search dream motifs for traditional auspicious / ominous meanings. For fun.

🀄

24 Solar Terms (二十四节气)

The 24 solar terms of the Chinese calendar — dates, meaning, customs and health tips.

Docs & Sheets

📝

Markdown Editor

Write Markdown with live preview, Mermaid diagrams, math formulas and HTML/PDF export — all in your browser.

📊

Online Spreadsheet

Edit Excel-like sheets in the browser: cells, formulas, charts, freeze panes with real XLSX/CSV import-export via SheetJS.

📄

PDF Tool — View, Merge, Split, Convert

View, merge, split, rotate, watermark, number pages and convert PDF & images in your browser via pdf.js + pdf-lib.

🔤

Rich Text Editor

A full-featured rich text editor with formatting, lists, links, code blocks and HTML export — Quill, 100% in browser.

📝

Word Document Editor

Import .docx/.html/.md/.txt, edit rich text, and export to DOCX/PDF/HTML/TXT — powered by mammoth.js + Quill + docx + html2pdf, 100% in browser.

🧊

CAD / DXF Viewer

Upload DXF files and view them in your browser with pan, zoom, layer toggle and PNG export.

🧊

3D CAD Viewer (STEP / IGES / BREP)

Upload STEP, IGES or BREP files and view them in 3D — parsed locally by OpenCASCADE WASM, rendered with Three.js. Rotate, zoom, wireframe and PNG export. No upload.

🧾

CSV Viewer / Editor

Paste or upload CSV, render it as an editable table, add rows/columns and export back — 100% in your browser.

🧊

Draw lines, rectangles, circles, arcs, ellipses, splines and text; import/export DXF (with ARC/ELLIPSE/SPLINE + layer colors), export SVG/PNG/JSON; zoom/pan, grid & object snap — 100% in your browser.

📄

Grid Paper Printable

Generate square / dot / hex / isometric / rice-cell grid paper and print or download as SVG / PNG.

📄

Tian Zi Ge Generator

Generate Chinese handwriting practice sheets with 田字格 / 米字格 / 九宫格 — tracing or empty mode.

📐

Subtitle Converter

Convert between SRT / WebVTT / ASS / SSA subtitles in your browser, with optional timeline offset (shift all cues by N seconds or milliseconds). Pure text parsing, no library.

Whiteboard & Drawing

🖌️

Whiteboard (Excalidraw)

An infinite hand-drawn style canvas for diagrams, arrows, notes and images. Export PNG, SVG or JSON.

🖌️

Drawing Pad

A simple freehand canvas: brush color and size, eraser, undo and PNG export.

✍️

Signature Pad

Sign with mouse or touch and export a clean PNG image.

🖌️

Offline Whiteboard

A dependency-free canvas whiteboard: pen, shapes, text, eraser, undo and PNG export — runs fully offline in your browser.

🖌️

Mind Map

Write a Markdown outline and get a live mind map, then export as SVG — powered by markmap, 100% in your browser.

🖌️

XMind / Mind Map Editor

An interactive mind-map editor — add child/sibling nodes, edit, drag, export JSON — powered by jsMind, 100% in your browser.

🖌️

draw.io Diagram Editor

Draw flowcharts, architecture, UML and more with the full draw.io editor — files stay in your browser, never uploaded.

📽️

Online Slides (PPT)

Write slides in Markdown and present instantly with reveal.js — live preview, fullscreen mode, PDF / print export, 100% in your browser.

Crypto

🔑

AES / DES / 3DES Encrypt & Decrypt

Symmetric encryption with AES, DES or 3DES, fully in your browser.

🔑

RSA Encrypt / Decrypt & Key Pair

Generate an RSA key pair, encrypt with the public key, decrypt with the private key.

🔐

JWT Decoder

Decode JWT tokens and inspect header and payload in your browser.

📝

Cisco Type 7 Password

Encrypt and decrypt Cisco Type 7 passwords (the weak 'enable secret 7' format) — 100% in your browser.

🔑

PEM Certificate Viewer

Parse a PEM-encoded X.509 certificate and inspect subject, issuer, validity, serial and SAN — powered by node-forge, 100% in your browser.

🔐

Hash Type Identifier

Identify the likely hash algorithm (MD5, SHA-1/256/512, bcrypt, NTLM, etc.) from a hash string — 100% in your browser.

🔑

RC4 Encrypt / Decrypt

Pure-JS RC4 stream cipher — KSA + PRGA implemented by hand. Output as hex or Base64. For learning and legacy compatibility only.

CSS Tools

🎨

CSS Cubic Bezier Generator

Visually create CSS cubic-bezier() easing curves with a live animation preview.

🎨

CSS Gradient Generator

Create linear, radial and conic gradients with live preview and copy-ready CSS — 100% in your browser.

🎨

Glassmorphism Generator

Build frosted-glass cards with backdrop-filter, live preview and copy-ready CSS, 100% in your browser.

🎨

Neumorphism Generator

Create soft-UI / Neumorphism cards and buttons with dual box-shadows — live preview and copy-ready CSS.

🔐

Box / Text Shadow Generator

Build box-shadow or text-shadow with multiple stacked layers — live preview and copy-ready CSS.

🎨

Flexbox Layout Visualizer

Tune flex-direction, justify-content, align-items, flex-wrap and gap with a live preview — copy-ready CSS.

🎨

CSS Grid Layout Visualizer

Tune grid-template-columns, gap and item alignment with a live preview — copy-ready CSS.

🎨

CSS Animation / @keyframes Generator

Twelve ready-made @keyframes presets with live preview and copy-ready CSS — duration / delay / iteration / easing all adjustable.

🎨

CSS Gradient Text

Turn any text into a CSS gradient with background-clip: text — live preview and copy-ready CSS.

Code Format

✨

Code Formatter & Minifier

Beautify or minify JS, CSS, HTML, JSON, Markdown and more with Prettier.

✨

Universal Code Tidy

Convert tabs/spaces, trim trailing whitespace, collapse blank lines and strip comments for any language — 100% in your browser.

🧾

SQL Formatter & Beautifier

Beautify and format SQL queries for MySQL, PostgreSQL, SQLite and more.

🧾

XML Formatter & Validator

Format, beautify, minify and validate XML in your browser.

✨

GraphQL Formatter

Beautify or minify GraphQL queries with a lightweight built-in tokenizer — no external library.

✨

Code Highlighter

Paste code, pick a language, get highlight.js-colored HTML ready to copy into PPTs or blog posts.

🔐

HTML Entities Escape

Escape text to HTML entities and back, with an extended named-entity cheat sheet.

Code Convert

🔄

curl to Code Converter

Convert a curl command into Python (requests), JavaScript (fetch), Node.js (axios), PHP (curl) and Go (net/http) code — 100% in your browser.

🏗️

HTML Live Preview

Write HTML/CSS/JS on the left and see the rendered result live on the right — 100% in your browser.

🔄

Robots.txt Generator

Compose User-agent, Allow/Disallow, Crawl-delay and Sitemap rules with one-click presets — preview, copy and download.

🧾

Sitemap.xml Generator

Turn a list of URLs into a standards-compliant sitemap.xml with lastmod, changefreq and priority — preview, copy and download.

🔄

SEO Meta Tag Generator

Generate title, description, OpenGraph, Twitter card, canonical and keywords meta tags, plus a Google SERP preview.

🏗️

HTML ↔ JS / JSX / PHP Converter

Convert HTML between document.write, JS template literals, JSX, and PHP echo — and back. Pure client-side.

🧾

JSON to Multi-Language

Generate Swift / Kotlin / Dart / Rust / Ruby / PHP / Scala type definitions from JSON.

Web Dev & Debug

🛠️

Keyboard KeyCode Finder

Press any key to instantly see its keyCode, code, key, and location.

🛠️

Cookie / Header Parser

Parse Cookie strings or HTTP headers into a key-value table, edit and export back — 100% in your browser.

🌐

HTTP Status Codes Reference

Searchable reference of HTTP response status codes (1xx–5xx) with meanings — 100% in your browser.

🛠️

MIME Type Lookup

Look up the MIME type for a file extension, or find extensions by MIME — 100% in your browser.

🛠️

User-Agent Parser

Decode a User-Agent string into browser name + version, layout engine, OS, device type and brand — pure front-end, powered by ua-parser-js.

🛠️

WebSocket Tester

Connect to ws:// or wss:// endpoints, send and receive messages, and inspect a timestamped, color-coded log — 100% in your browser.

🛠️

Punycode / IDN Converter

Convert internationalized domain names to/from ACE (xn--) Punycode, with per-label and batch mode — built-in RFC 3492 with CDN fast path.

🛠️

Disk Partition Integer-Size Calculator

Compute the exact MB value to type into Windows Disk Management so the result shows as a clean integer GB — three formulas compared.

🛠️

Linux Command Reference

100+ common Linux commands with English and Chinese summaries, examples and category filters — fully in your browser.

🛠️

XPath Tester

Paste XML or HTML, write an XPath expression, run it with the browser's native document.evaluate and inspect every matched node.

🔋

Screen Pixel Ruler

On-screen pixel ruler with horizontal & vertical guides. Measure distance in px and estimated mm. Pure front-end.

📊

Regex Cheat Sheet

Quick reference for JavaScript / PCRE-style regular expressions: metacharacters, character classes, quantifiers, anchors, groups, lookarounds, flags and common patterns.

🛠️

API Tester

A Postman-like HTTP client that runs fully in your browser — build params / headers / body and inspect the response.

Security & Hash

🔐

JavaScript Obfuscator

Obfuscate JS code to protect your source in the browser.

🔐

File Hash Calculator

Compute SHA-1/256/384/512, MD5 and CRC32 hashes of any file, entirely in your browser — large files are processed incrementally so the tab stays responsive.

🔐

Magic Bytes / File Header Lookup

Identify a file type from its first bytes, or look up the magic signature of an extension — 30+ common signatures built in, pure front-end.

🔐

htpasswd Generator

Generate Apache .htpasswd lines with BCrypt (recommended), APR1 (MD5 crypt) or SHA1 — pure front-end, nothing uploaded.

🔐

CSR Generator

Generate a Certificate Signing Request (CSR / PKCS#10) and RSA private key locally in your browser with node-forge. Nothing is uploaded.

🗜️

Gzip Compress / Decompress

Text ⇄ gzip ⇄ Base64 in your browser using the native CompressionStream API. No upload, no server.

📝

Password Strength Checker

Check password strength in real time: length, character sets, estimated entropy and improvement tips — 100% in your browser, nothing is uploaded.

Image & Media Editing

🖼️

Image Compressor

Compress PNG, JPG and WebP images in your browser with adjustable quality.

🖼️

SVG Formatter & Viewer

Format, minify and preview SVG images in your browser.

🖼️

Image Editor

Edit images with brush, shapes, text, filters and crop — powered by Fabric.js, 100% in your browser.

🔤

Online Photoshop (PS Editor)

Pro-grade photo editing with layers, adjustments, filter presets, transforms and PNG/JPG/WebP export — powered by Fabric.js, 100% in your browser.

🖼️

Photo Editor

Crop, rotate, flip, adjust colors, add stickers, text, masks and filters — powered by TOAST UI Image Editor, 100% in your browser.

🖼️

AI Background Remover

Automatically remove image backgrounds with an on-device AI model and export transparent PNG — zero upload, 100% in your browser.

🖼️

Image Watermark

Stamp text or image watermarks onto one or many pictures — single position or tiled.

🖼️

Metronome

A precise online metronome — BPM 40–240, 2/3/4/6 time signatures, accented downbeat. Web Audio API lookahead scheduler, zero drift.

🗜️

Guitar Tuner

Detect the pitch of any monophonic sound via your microphone and an autocorrelation algorithm. Standard EADGBE + chromatic mode, ±50 cent deviation meter.

🖼️

Audio Cutter

Trim audio (mp3 / wav / m4a / ogg) right in your browser. Drag the start / end markers on the waveform, optionally add fade in / out, then export a standard 16-bit PCM WAV via OfflineAudioContext.

Image Convert & Generate

🖼️

Image Format Converter

Convert PNG, JPG, WebP, BMP and GIF (first frame) between each other with a quality slider.

🎨

ICO Icon Maker

Upload a PNG and generate a multi-resolution .ico favicon (16–256px), 100% in your browser.

🖼️

Placeholder Image Generator

Generate PNG or SVG placeholder images with custom size, text, background and text color.

🎨

Grid Image Slicer

Slice an image into 2×2, 3×3 or 3×4 tiles for Moments / Xiaohongshu montages.

🗜️

Festival Avatar Maker

Upload a photo and stamp a festival theme — National Day, Christmas, Spring Festival, Mid-Autumn — drawn purely with Canvas.

🎨

Meme Generator

Stamp classic Impact-style top/bottom text onto an uploaded image or a built-in template. 100% in your browser.

🖼️

GIF Split / Extract Frames

Decode an animated GIF into individual PNG frames — each shown with index and delay, downloadable one-by-one or all at once.

🖼️

GIF Crop

Crop an animated GIF with a draggable selection; every frame is cropped and re-encoded preserving delays.

🖼️

GIF Resize / Scale

Resize or scale an animated GIF to a new width/height (with optional aspect-ratio lock) and re-encode preserving delays.

🎨

Color Palette Library

Curated palettes — Material Design, Tailwind, brand colors, CSS gradients, and Chinese / Japanese traditional colors. Click a swatch to copy its hex.

🎨

CSS Sprites Generator

Merge many small icons into one PNG sprite sheet + generate .icon CSS classes with background-position.

🎨

Maze Generator

Generate solvable N×M mazes with recursive-backtracking DFS, optional BFS shortest-path solve, PNG / SVG export.

🎨

Color Blindness Test

Ishihara-style color plates generated on canvas. Read the hidden digit to screen for normal / red-blind / green-blind vision.

Network & IP

🌐

Subnet / IP Calculator

Calculate network, broadcast, host range and subnet mask from an IP and CIDR.

🌐

Proxy Node Parser

Parse VMess, VLESS, Trojan and Shadowsocks node URIs into a readable field table — 100% in your browser. Nothing is sent anywhere.

🌐

Magnet Link Parser / Generator

Parse a magnet URI into its info-hash, name, trackers and size, or build one from a hash — 100% in your browser.

🌐

IPv4 Address Converter

Convert an IPv4 address to/from decimal, binary, hex and octal — 100% in your browser.

🌐

IP / MAC Address Generator

Batch-generate random IPv4, IPv6 and MAC addresses — private ranges, vendor OUI and custom separators.

Math Calculators

🧮

Scientific Calculator

Evaluate expressions with trigonometry, logarithms, powers and constants — powered by math.js, 100% in your browser.

🧮

Fraction Calculator

Add, subtract, multiply and divide fractions, with simplification, decimal value, GCD / LCM helpers and step-by-step working.

🧮

Fraction Reducer

Reduce fractions to lowest terms via GCD with steps shown, convert improper ↔ mixed, and compare fractions by common denominator.

🧮

Percentage Calculator

Four common percentage modes — what is X% of Y, ratio, growth rate, and reverse.

🧮

BMI Calculator

Body Mass Index with China / WHO thresholds, healthy weight range and an optional U.S. Navy body-fat estimate — 100% in your browser.

🎲

Dice Roller

Roll D4 / D6 / D8 / D10 / D12 / D20 / D100, any count from 1 to 20, with totals, max/min, average and a rolling history — pure front-end.

🧮

Coin Flip

Flip a 3D animated coin for heads-or-tails decisions, with live stats and streak tracking.

🧮

Reaction Time Test

Click when the pad turns green. 5 / 7 / 10 rounds, full stats, early-click detection. Personal best saved locally.

🧮

Roman Numerals Converter

Convert between Arabic numbers (1–3999) and Roman numerals — 100% in your browser.

📐

RMB Currency Uppercase

Convert an Arabic-numeral amount into Chinese RMB uppercase (壹仟贰佰…元整).

🔤

Chart Generator

Draw pie / bar / line / scatter / radar charts on a pure canvas — no chart library, with CSV paste and PNG export.

🎲

Number Format

Convert a number into thousands, scientific, Chinese, percent, fixed precision and ordinal forms, live.

🧮

Sort Algorithm Visualizer

Hand-rolled bubble / selection / insertion / quick / merge / heap sort with canvas animation and step statistics.

🧮

GCD & LCM Calculator

Greatest common divisor and least common multiple of several integers, with prime factorization.

🧮

Permutation & Combination

P(n,k), C(n,k), n^k, with-repetition variants and factorial — exact BigInt results.

🧮

24 Point Game

Find every way to make the target from four numbers using + − × ÷ and parentheses.

🧮

BMR / TDEE Calculator

Calculate your Basal Metabolic Rate and Total Daily Energy Expenditure with the Mifflin-St Jeor equation, plus daily calorie targets for losing, maintaining or gaining weight — 100% in your browser.

🧮

GPA Calculator (4.0 Scale)

Calculate your semester or cumulative GPA on the 4.0 scale. Add courses with letter grades (A, A−, B+, …) or percentages and credits — the GPA updates live, 100% in your browser.

🧮

Geometry Calculator (Area / Perimeter / Volume)

Calculate the area, perimeter and volume of common shapes (circle, square, rectangle, triangle, cube, cuboid, sphere, cylinder) — 100% in your browser.

🧮

Ratio Calculator — Solve Proportions A:B = C:D

Solve proportions A:B = C:D (leave one field blank to auto-solve), simplify ratios, and convert between ratios, fractions, decimals and percentages — 100% in your browser.

Unit & Measurement

📐

Unit Converter

Convert between length, weight, temperature, area, volume, speed, data and time units — 100% in your browser.

🧮

PPI Screen Density Calculator

Calculate pixels per inch (PPI), total pixels, aspect ratio and dot pitch from screen resolution and diagonal size.

📅

Data Storage Converter

Convert between bit / Byte / KB / MB / GB / TB / PB / EB with both binary (1024) and decimal (1000) standards.

📐

Geo Distance Calculator

Great-circle distance (Haversine) and bearing between two lat/lng points, with multi-leg path total. Earth radius = 6371 km.

📐

Standard Carton Size Calculator

Recommend a standard carton size for your product and compute volume + dim-weight for shipping.

📐

Paper Size Reference

Look up ISO A/B/C, US Letter/Legal/Ledger and Chinese paper sizes, or match your own dimensions.

🔤

Size Chart Converter

Cross-reference clothing, shoes, underwear and ring sizes across regions.

📅

Voltage & Plug Reference

Mains voltage, frequency and plug type for 80+ countries and regions — for travel and cross-border appliances.

📐

Cooking Converter

Convert between cups, tablespoons, teaspoons, milliliters, grams and ounces for water, flour, sugar, butter, rice, oil and more — each ingredient uses its own density for accurate volume-to-weight conversion. 100% in your browser.

📐

Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin and Rankine — enter one value and the other three update live. 100% in your browser.

🧮

Dilution Calculator (C1V1 = C2V2)

Calculate the final volume and solvent to add when diluting a solution, using the C1V1 = C2V2 formula. Supports multiple concentration and volume units — 100% in your browser.

Finance & Reference

💰

Personal Income Tax Calculator

China cumulative withholding method for salary income with the 2024 seven-bracket progressive rate table — 100% in your browser.

📅

Mortgage Calculator

Calculate monthly payments, total payment and total interest with equal-payment or equal-principal methods — 100% in your browser.

⏰

Multi-Channel Timer

Run several independent count-up / count-down timers side by side, each with its own start / pause / reset, plus a beep + flash when a countdown hits zero.

⏰

Pomodoro Timer

Work–break cycles (25/5/15 by default) with auto phase switching, Web Audio beep and optional browser notifications — 100% client-side.

💰

What To Eat Today

A wheel of 30+ common cuisines — Chinese, Western, fast food, Japanese, hotpot, BBQ and more. Edit the list, exclude what you don't want, and spin. History is kept locally.

💰

Blood Type Inheritance Lookup

Look up child ABO blood types from parents, or infer the other parent's possible type.

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Chinese Kinship Title Calculator

Build a relationship chain from "me" and get the Chinese title, what they call you, and English.

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Periodic Table of Elements

Interactive 118-element periodic table with category coloring, search and click-for-detail.

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Chinese Dynasties Timeline

Major Chinese dynasties with years, capitals, founders and key events.

💰

World Capitals Lookup

Capitals, currencies, languages and dial codes for 150+ countries and regions.

💰

China Universities Lookup

Search 985 / 211 / Double First-Class universities by name, province or tag.

💰

Top-Level Domain (TLD) Lookup

100+ common TLDs with meaning, category, country and usage notes.

💰

Handheld Danmu Banner

Turn any text into a huge scrolling banner — for concerts, airport pickups and fan signs.

🌐

Passport Number Validator

Real-time format check for 15+ countries' passport numbers, with a built-in regex rule table and valid samples.

📝

Currency Amount in Words

Convert a number into uppercase words for USD, EUR, JPY, GBP, KRW, CNY and 10+ currencies — 100% in your browser.

💰

Compound Interest

Future value with principal, rate, years, recurring contributions and compounding frequency.

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Bank Card BIN Lookup

Enter the first 6 digits of a Chinese bank card to identify the issuing bank and card type.

🎲

Number Fortune (81 数理)

Check a phone / plate / any number against the traditional 81-number fortune table.

💰

Loan Calculator (Equal Installment)

Calculate the fixed monthly payment, total interest and total repayment of an equal-installment (amortized) loan — 100% in your browser.

🎲

Discount Calculator

Calculate the final price after a percentage discount, or reverse the math to find the discount rate from the original and final price.

🧮

Fuel Cost Calculator

Calculate total fuel used and total fuel cost for a trip from distance, fuel consumption and fuel price, or estimate per-trip cost from tank size and one-way distance — 100% in your browser.

💰

Sales Tax / VAT Calculator

Add sales tax or VAT to a net price, or reverse it to extract the net price and tax amount from a tax-inclusive gross price.

🧮

Retirement Savings Calculator

Project your retirement nest egg from current age, savings, monthly contributions, annual return and inflation — see the nominal balance, real purchasing power and the monthly income the 4% safe-withdrawal rule supports. 100% in your browser.

🧮

Rent / Lease Cost Calculator

Calculate total lease cost (rent + deposit), rent-to-income ratio and deposit amount — with a 30% safety-line hint. Runs 100% in your browser.

Fitness & Weight Loss

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MET Exercise Calorie Calculator

Estimate calories burned during exercise with the Metabolic Equivalent of Task (MET) formula. Pick a built-in activity or enter a custom MET, then input your weight and duration — 100% in your browser.

🔧

Fat-Burn Follow-Along Workout

Follow a guided fat-burn workout — 10 built-in exercises (jumping jacks, squats, push-ups, burpees…) with automatic rest intervals, a big countdown, a demo animation and live calorie burn computed from MET × your weight. 100% in your browser, nothing uploaded.

Lab & Learning

🧮

Multiplication Table Generator

Generate a printable N×N multiplication table (1–20). Highlight the diagonal or any row/column, switch to practice mode for blank fill-in worksheets, and print a clean, controls-free copy. Runs entirely in your browser.

📊

Arithmetic Worksheet Generator

Generate printable addition, subtraction, multiplication and division worksheets with random problems — pick the operation, number range and count. 100% in your browser.

🔧

Triangle Solver (Sides, Angles, Area)

Solve any triangle from 3 knowns (SSS / SAS / ASA / AAS / SSA): compute the remaining sides and angles, area via Heron's formula, perimeter, angle-sum verification, and a scaled SVG drawing — 100% in your browser.

📈

Function Plotter

Plot math functions on a canvas with axes, grid and ticks. Supports sin, cos, tan, polynomials, square root, absolute value, exponential and logarithm — 100% in your browser.

🧮

Fraction Visualizer & Calculator (Pie / Bar + Operations)

Visualize a fraction as an SVG pie chart and bar, convert it to a decimal and percentage, simplify it with the GCD, and add, subtract, multiply or divide two fractions with common-denominator steps — all in your browser.

🔧

Binary Search Visualizer

Step-by-step binary search on a sorted array — watch the low / mid / high pointers move, comparisons highlighted, with a running step log. Pure front-end, no server, no upload.

🔧

Pathfinding Algorithm Visualizer

Hand-rolled BFS / DFS / A* on an interactive grid — draw walls, set start and end, and watch the search expand step by step with visited, frontier and path highlighting.

🔧

Stack Visualizer (LIFO)

Interactive stack data-structure visualizer. Push, pop, peek and clear with per-step animation, a live state readout, an operation log, and a walkthrough of bracket matching, undo and the call stack. Pure front-end, nothing uploaded.

🔧

Queue Visualizer (FIFO)

Interactive queue data-structure visualizer — enqueue at the tail, dequeue from the head, peek the front. Pure front-end, with a step log, live stats and real-world use cases.

🔧

Singly Linked List Visualizer

Step-by-step animation of a singly linked list: insert at head / tail / position, delete by value, search and reverse — with node + pointer diagrams, a live step log and the current list state. Runs entirely in your browser.

🃏

Flashcard Vocabulary Trainer

Memorize vocabulary with click-to-flip flashcards. Import your own word list or use the built-in sample, mark cards as known or unsure, and track learning progress. 100% client-side — your list and progress stay in your browser.

🔧

Grammar Quiz — Multi-Language Multiple Choice

Practise grammar with multiple-choice questions across English tenses, Chinese idioms and French / German / Spanish verbs. Pick an answer, get instant feedback (green / red) with an explanation, track your score and best result. Import your own questions via JSON. Runs entirely in your browser.

🔤

Text Recitation & Cloze Tool (Blank-and-Fill)

Paste a passage, choose how much to blank out (by character or word), fill the missing parts back in from memory, and get instant per-blank grading — perfect for recitation and dictation practice. Runs fully in your browser; nothing is uploaded.

🔧

Dictation & Memorization Tool

Practice writing text from memory — paste a poem, a lesson paragraph or vocabulary, memorize it for a few seconds, then write it from memory and get a character-by-character check with accuracy and a list of errors. 100% in your browser.

🔧

Ohm's Law Calculator (V = I × R)

Ohm's law calculator — enter any two of voltage (V), current (I), resistance (R) or power (P) and instantly solve the rest. Supports V/mV, A/mA, Ω/kΩ, W/mW unit conversion. Runs entirely in your browser.

🔧

Circuit Simulator — Series & Parallel Resistors

Simulate series and parallel resistor circuits: add resistors, set a source voltage and see total resistance, total current and the voltage or current through each resistor, with a live circuit diagram. Runs entirely in your browser.

🧮

Optical Refraction Simulator (Snell's Law)

Simulate light refraction between two media. Enter the incident angle and refractive indices n₁/n₂ to compute the refraction angle via Snell's law, visualize the incident, refracted and reflected rays plus the normal, and detect total internal reflection with the critical angle. 100% client-side.

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Wave Visualizer

Interactive sine / square / triangle / sawtooth wave plotter. Set amplitude, frequency (Hz) and phase, then overlay a second wave to see interference and the resulting sum — rendered live on canvas, 100% in your browser.

🔧

Chemical Equation Balancer

Balance chemical equations instantly. Enter an unbalanced reaction like H2+O2=H2O and get the smallest whole-number coefficients (e.g. 2H2+O2=2H2O) with a per-element conservation check. Supports common elements and parentheses such as Ca(NO3)2 — 100% in your browser.

🔧

Frontend Interview Quiz

Practise common frontend interview questions with multiple choice: JavaScript (closures, event loop, this, prototypes, ES6), CSS (box model, Flex, Grid), the browser (rendering, events, storage) and React / Vue basics. Pick an answer, get instant feedback (green / red) with an explanation, track your score and best result. Runs entirely in your browser.

🔧

Backend Interview Quiz — Multiple Choice

Practise backend interview multiple-choice questions on database indexes / transactions / ACID, messaging and Kafka / Redis, concurrency and locks, caching strategy, networking (TCP / HTTP / HTTPS) and microservice basics. Pick an answer, get instant feedback (green / red) with an explanation, track your score and best result. Import your own questions via JSON. Runs entirely in your browser.

🔧

Algorithm Interview Quiz — Multiple Choice

Practise algorithm-interview multiple-choice questions on time/space complexity, arrays & linked lists, trees & graphs, sorting algorithms, and techniques (binary search, two pointers, sliding window, dynamic programming). Pick an answer, get instant feedback (green / red) with an explanation, track your score and best result. Import your own questions via JSON. Runs entirely in your browser.

✍️

System Design Interview Quiz

Practise system-design interview questions with multiple choice: load balancing, caching/CDN, database sharding & replication, microservices, message queues, CAP/BASE, rate limiting & circuit breaking, and scalability principles. Pick an answer, get instant feedback (green/red) with an explanation, track your score and best result. Runs entirely in your browser — nothing is uploaded.

🔧

Soft-Skills / Management Interview Trainer

Practise behavioural and management interview questions across leadership, team management, conflict, decision-making, strategic thinking, prioritisation, communication, product thinking, technical management and cross-functional collaboration. Read each scenario, pick the BEST response, get instant feedback (green / red) with an explanation, track your score and best result. Runs entirely in your browser — nothing is uploaded.

🔧

Sunrise / Sunset Calculator

Compute sunrise, sunset, solar noon, day length and the solar elevation angle for any location and date using standard NOAA solar astronomy (solar declination, equation of time, hour angle) — runs entirely in your browser.

📐

Coordinate Converter

Convert between decimal degrees and degrees/minutes/seconds — supports latitude (N/S) and longitude (E/W), live both ways. 100% in your browser.

🎨

Resistor Color Code Reader (4 / 5 Band)

Read 4-band and 5-band resistor color codes online: pick the band colors to get the resistance value and tolerance, or enter a value to see the matching color bands. Live SVG preview, 100% client-side.

🧮

pH Calculator — pH / pOH / [H⁺] / [OH⁻]

Enter [H⁺], [OH⁻] or a pH value to compute pH, pOH, [H⁺] and [OH⁻], with an acid / neutral / base verdict (pH = −log₁₀[H⁺], pOH = 14 − pH, Kw = 10⁻¹⁴). Supports back-calculating [H⁺] from pH — 100% in your browser.

🔧

Molar Mass Calculator

Calculate the molar mass (molecular weight) of any chemical formula. Enter H2O, C6H12O6, Ca(OH)2 or Fe2(SO4)3 to get the result in g/mol plus the mass fraction of every element, with full support for parentheses and subscripts — runs entirely in your browser.

🔧

DNA Sequence Tool — Transcription, Translation & Complement

Online DNA sequence tool: enter a DNA strand like ATGCATG to get the complementary strand (A↔T, G↔C), the transcribed mRNA (T→U) and the translated amino-acid chain using the standard genetic code (64 codons, including start and stop). Case-insensitive; non-ATGC characters are skipped. Runs entirely in your browser — data never leaves your device.

🔧

Electron Configuration Calculator

Enter an element symbol (e.g. Na, Fe) or atomic number (1–118) to get the Aufbau electron configuration (1s² 2s² 2p⁶…), an orbital box diagram (↑↓ per orbital), the valence electron count and the period / group — 100% in your browser.

🔧

Binary Tree Traversal Visualizer

Build a binary search tree from a list of numbers and watch pre-order, in-order, post-order and level-order (BFS) traversal animate step by step on an SVG, with the visit sequence and a step-by-step log. 100% client-side.

🔧

Binary Heap Visualizer (Max / Min Heap)

Animated binary heap visualizer — switch between max-heap and min-heap, insert a value (append + sift-up / heapify-up), extract the top (sift-down / heapify-down), and run a one-click heap-sort demo. Every comparison and swap is highlighted step-by-step on an SVG tree and the parallel array view, with a live step log. Pure front-end — nothing is uploaded.

🔤

Number Line Visualizer

Interactive SVG number line for elementary math: plot points, show addition and subtraction as jumps, measure distance and absolute value, and highlight inequality intervals. Adjustable range with integer or decimal ticks — 100% in your browser.

🔧

Probability & Statistics Calculator

Compute mean, median, mode, variance, standard deviation, range, sum and count from a dataset, plus coin-flip and dice-roll probability simulations — 100% in your browser.

🧮

Regular Polygon Calculator

Enter the number of sides (3–100) and side length to compute the interior angle sum, each interior/exterior angle, perimeter, area, apothem and circumradius, plus an SVG drawing — 100% in your browser.

🔧

Pendulum Period Simulator

Set the pendulum length L, initial angle θ and gravity g to get the period T = 2π√(L/g) (small-angle approximation), frequency and angular frequency, with a live SVG animation of the swing and real-time angle, height, velocity and kinetic / potential energy readings. Runs entirely in your browser.

🔧

Punnett Square Calculator

Free Punnett square calculator: enter the parents' genotypes (e.g. Aa × Aa or AaBb × AaBb) to generate the Punnett square grid plus offspring genotype and phenotype ratios with counts, fractions and probabilities — runs entirely in your browser.

🔧

English Vocabulary Quiz — CET4 / CET6 / IELTS / TOEFL / SAT

Practise English vocabulary with multiple-choice questions: pick the closest synonym or meaning for high-frequency words across CET4, CET6, IELTS, TOEFL and SAT. Choose an answer, get instant feedback (green / red) with a meaning and example sentence, track your score and best result. Import your own questions via JSON. Runs entirely in your browser.

🔧

Conic Section Visualizer

Interactive conic section plotter — draw ellipses, hyperbolas, parabolas and circles on a canvas with axes, foci, vertices, asymptotes and directrix annotated, plus the standard equation, eccentricity and focal length. Pure front-end, no upload.

🔧

RLC Circuit Calculator (Resonant Frequency, Impedance, Q Factor)

RLC circuit calculator — enter resistance R, inductance L and capacitance C to compute the resonant frequency f₀ = 1/(2π√LC), angular frequency ω₀, quality factor Q = (1/R)√(L/C) and the impedance at resonance. Supports Ω/kΩ/MΩ, H/mH/µH and F/µF/nF/pF. Runs entirely in your browser.

🔧

Convex Lens Imaging Simulator (Thin Lens)

Simulate image formation by a thin convex (converging) lens. Enter the focal length f and object distance u; the tool applies the thin-lens equation 1/f = 1/u + 1/v to find the image distance v, the magnification M = −v/u, and the image nature (real/virtual, inverted/upright, magnified/diminished). It draws the lens, principal axis, object, image and the three principal rays (parallel ray through F′, ray through the optical center, ray through F exiting parallel). 100% client-side, nothing uploaded.

🧮

Lever Principle Calculator (F₁ × L₁ = F₂ × L₂)

Lever principle calculator — enter any three of effort (F₁), effort arm (L₁), load (F₂) or load arm (L₂) and instantly solve the fourth. Shows the lever type (effort-saving, effortful or balanced) and draws an SVG diagram. Runs entirely in your browser.

🔧

Probability Distribution Calculator — Normal / Binomial / Poisson

Compute and plot Normal, Binomial and Poisson probabilities — enter the parameters and get the PDF/PMF, cumulative probability and a distribution chart. Runs entirely in your browser.

🧮

Vector Calculator (2D / 3D)

Online vector calculator — enter the components of two vectors (x, y, z) and choose add, subtract, dot product or cross product. Shows the result vector, magnitude, unit vector and the angle between the vectors, with an optional 2D plot. 100% in your browser, nothing uploaded.

🎲

Complex Number Calculator (Add / Subtract / Multiply / Divide)

Online complex number calculator: enter two complex numbers a+bi and c+di, choose add, subtract, multiply or divide, and get the result in rectangular form plus magnitude, argument and polar form. 100% in your browser.

🧮

Matrix Calculator (Add / Subtract / Multiply / Transpose / Determinant)

Add, subtract, multiply, transpose and find the determinant of 2–4×2–4 matrices — with dimension validation, 100% in your browser.

🔧

Fourier Series Visualizer

Interactive Fourier series synthesizer. Pick a square / triangle / sawtooth wave, set the number of harmonics N (1–50), and watch the sum of N sine harmonics converge to the target wave on a live canvas — with the frequency spectrum, per-harmonic coefficients and the Gibbs phenomenon overshoot. Pure front-end, nothing leaves your browser.

🔧

Newton's Laws Calculator (F = m·a + Gravitation)

Newton's laws calculator — Newton's second law F = m·a (enter any two of force, mass, acceleration to solve the third) and universal gravitation F = G·m₁·m₂/r² (G = 6.674×10⁻¹¹). Supports N/kN/dyn/lbf, kg/g/t/lb, m/s²/g, Earth/Solar mass and AU. Runs entirely in your browser.

📈

Graph Traversal Visualizer (BFS / DFS)

Build an undirected node-and-edge graph by hand or load a preset, pick a start node, then watch hand-rolled BFS / DFS expand step by step with the current node, visited set and live queue / stack highlighted. Pure front-end SVG + JS, data never leaves your browser.

🔧

Operating System Concepts Quiz — Multiple Choice

Practise multiple-choice questions on core operating-system concepts for interviews: processes & threads, CPU scheduling, memory / paging / virtual memory, deadlock, file systems, I/O management and synchronization. Pick an answer, get instant feedback (green / red) with an explanation, track your score and best result. Import your own questions via JSON. Runs entirely in your browser.

🌐

Network Protocol Interview Quiz — Multiple Choice

Practise networking interview questions on the OSI / TCP-IP model, TCP vs UDP, the three-way handshake and four-way teardown, HTTP / HTTPS / TLS, DNS, routing & NAT and congestion control. Pick an answer, get instant feedback (green / red) with an explanation, track your score and best result. Import your own questions via JSON. Runs entirely in your browser.

🧮

Numerical Integral Calculator

Compute definite integrals ∫ₐᵇ f(x) dx with Simpson's 1/3 rule or the trapezoidal rule, and visualize the curve and the filled area on a canvas. Supports sin, cos, polynomials, sqrt, exp, log and more — 100% in your browser.

🧮

Numerical Derivative & Tangent Line Calculator

Enter a function f(x) and a point x₀ to compute the numerical derivative f′(x₀) with central differences (f(x+h)−f(x−h))/2h, get the tangent-line equation y=f′(x₀)(x−x₀)+f(x₀), and draw the curve together with its tangent on a canvas. Slide x₀ to watch the tangent update in real time — 100% in your browser.

⚖️

Differential Equation Solver (Euler / RK4)

Numerically solve the first-order ODE dy/dx = f(x, y) from an initial point (x₀, y₀) with Euler's method and the fourth-order Runge–Kutta (RK4) method. Input the step size h and the number of steps, then compare both solution curves on a canvas. Supports sin, cos, exp, polynomials and more — 100% in your browser, nothing uploaded.

🧾

SQL Interview Quiz — Multiple-Choice Questions

Practise SQL interview questions as multiple choice: SELECT/WHERE, GROUP BY/HAVING, JOIN types, indexes, transactions, subqueries, aggregates and window functions. Pick an answer, get instant feedback (green/red) with an explanation, then move on. Your score and best result are saved locally. Runs entirely in your browser — nothing is uploaded.

🔧

Set Theory & Venn Diagram Tool (Union, Intersection, Difference)

Enter two sets A and B (and an optional universe U) to compute the union, intersection, difference, complement and symmetric difference, with cardinalities and an SVG Venn diagram that highlights each result. Runs entirely in your browser.

🔧

Boolean Algebra — Truth Table & Logic Simplification

Online boolean algebra calculator: enter an expression with AND, OR, NOT, XOR, NAND, NOR and variables A-D to generate the full truth table, minterms and maxterms, canonical SOP/POS, the Quine-McCluskey minimized SOP, and a logic-gate diagram. Runs entirely in your browser.

🔧

Polynomial Root Finder

Find all roots of a polynomial of degree 2–6. Quadratics use the closed-form x=(−b±√(b²−4ac))/2a with the discriminant Δ=b²−4ac; degrees 3–6 use the Durand–Kerner numerical method to find every real and complex root, then plot the curve with the real roots marked — 100% in your browser.

🔧

Compiler Lexer Visualizer — Lexical Analysis of Source Code

Online compiler lexer (scanner) visualizer: paste a code snippet and watch it tokenized in real time into keywords, identifiers, numbers, strings, operators, delimiters and comments. Each token is colour-coded, listed with its type and value, and counted. Keyword presets cover C/C++, Java, JavaScript and Python. A regex-free state machine runs entirely in your browser — nothing is uploaded.

🧮

Prime Factorization & Prime Number Tool

Online prime factorization tool: enter a positive integer N to factorize it (e.g. 60 = 2² × 3 × 5), test whether N is prime, list every prime up to N via the Sieve of Eratosthenes, and count primes ≤ N (π(N)). 100% in your browser.

🔧

Kinetic / Potential / Mechanical Energy Calculator

Online physics energy calculator — compute kinetic energy KE = ½mv², gravitational potential energy PE = mgh, and the total mechanical energy ME = KE + PE. Supports kg/g, m/s/km/h, m/cm units. Runs entirely in your browser.

🖌️

ER Diagram Builder (Database Entity-Relationship)

Build database entity-relationship (ER) diagrams in your browser. Add entities with attributes and mark primary (PK) / foreign (FK) keys, connect two entities with 1:1, 1:N or M:N cardinality, and the diagram renders live in SVG with crow's-foot notation. Drag tables, edit or delete entities and relations, load a sample schema. Pure front-end — your schema never leaves the browser.

🧮

Bitwise Calculator — AND / OR / XOR / NOT / Shift + Binary Visualization

Online bitwise calculator: enter two integers and choose AND, OR, XOR, NOT, left shift or right shift to get the result in decimal, binary and hexadecimal, with a per-bit grid that highlights set and differing bits. Runs entirely in your browser.

Developer Tools

🎨

Office & Documents

📄

Screen & Display

🎨

Date & Life

🎂

Text Tools

🔢

Converters & Calculators

📐

Generators

📱

Fun & Divination

🔮