Free Dev Tools
145 developer utilities you can use right in your browser — JSON, JWT, Base64, regex, hash, UUID… No install, no sign-up, no data sent anywhere.
Code & Data
Format, validate, and convert JSON, YAML, XML, CSV, SQL, and more, plus regex, diff, cron, UUID, and other coding utilities.
JSON Format / Validate
Format, validate, and minify JSON. Highlights syntax errors.
JSON ↔ YAML
Two-way conversion between JSON and YAML (supports maps, lists, nesting, and scalars).
JSON ↔ CSV
Convert an array of objects to and from CSV (correctly handles commas, double quotes, and line breaks inside cells).
JSON ↔ XML
Two-way JSON ↔ XML conversion. Attributes use @, text content uses #text.
JSON → TypeScript
Generate a TypeScript interface from a JSON sample (merges keys, infers types, handles nesting).
SQL Formatter
Format SQL statements: capitalizes keywords, breaks lines by clause, and indents AND/OR/ON.
Minify JS / CSS
Minify JS/CSS (strips comments, collapses whitespace, combines into a single line). Inserts semicolons per ASI rules for JS so the code doesn't break.
.env Parser
Parse .env files to and from JSON (supports export prefixes, quotes, and trailing comments).
UUID Generator
Generate UUID v4 values (cryptographically secure). Create them in bulk.
Regex Tester
Test regular expressions, with highlighted matches and capture groups.
Text Diff
Compare two blocks of text line by line (LCS algorithm).
Side-by-Side Diff
Compare two texts displayed side by side, line by line (LCS algorithm).
Markdown Preview
Instantly preview Markdown as HTML (headings, lists, code, links, blockquotes, and more).
Number Base Converter
Binary / Octal / Decimal / Hex, with a quick conversion tester.
Unix Timestamp
Convert between Unix epoch time and human-readable dates (seconds and milliseconds).
Cron Explainer
Explains 5-field cron expressions in plain English and lists the next run times.
JSON Escape/Unescape
Escape text into a valid JSON string, or unescape a JSON string back to the original text.
Text ↔ Binary
Convert text to 8-bit binary and back (UTF-8).
Hex ↔ Text
Convert text to hex code and back (UTF-8).
Chmod Calculator
Calculate Unix permissions: check r/w/x for owner/group/other to get the octal number and rwx notation.
Roman Numerals
Convert between regular numbers (1-3999) and Roman numerals.
Byte Size Converter
Convert data sizes: decimal (KB/MB/GB, x1000) and binary (KiB/MiB/GiB, x1024).
XML Format / Validate
Format, minify, and validate XML syntax.
JSON → Code
Generate Go structs, C#, Java, and Python classes from sample JSON.
Code Beautifier
Beautify (un-minify) JavaScript, CSS, and HTML code.
Fake Data Generator
Generate fake data — names, emails, phone numbers, addresses — as JSON or CSV.
Gzip Compress / Decompress
Compress and decompress gzip/deflate via Base64.
cURL Converter
Convert curl commands into Python, JavaScript, Go, or PHP code.
SQL Diff Checker
Compare two SQL statements line by line, with differences highlighted.
JSON Compare
Compare two JSON documents semantically and list every difference by path.
JSON Schema Validator
Check whether JSON is valid against a JSON Schema (draft-07).
YAML Validator
Validate YAML syntax and instantly view the matching JSON.
TOML to JSON
Convert TOML configuration into JSON format instantly.
CSV Viewer
View CSV files as a table and quickly sort by any column.
CSV Compare
Compare two CSV files line by line, with differences highlighted.
CSV Merge
Merge multiple CSV files vertically or horizontally in seconds.
CSV Splitter
Split a CSV file by row count, automatically keeping the header row.
HTML to Markdown
Convert HTML code into clean Markdown while preserving the structure.
Regex Explainer
Get a detailed, plain-English breakdown of every part of a regex pattern.
Cron Expression Builder
Visually build cron expressions with an easy-to-read schedule description in plain English.
Docker Compose Generator
Generate a complete docker-compose.yml file from an easy visual form.
Nginx Config Generator
Generate a complete Nginx server block configuration from a simple form.
NanoID Generator
Generate batches of URL-safe NanoIDs with a custom length.
ULID Generator
Generate sortable, timestamp-based ULIDs and decode the timestamp from any ULID.
SEO & Marketing
Meta tags, Open Graph, robots.txt, sitemap, hreflang, UTM builder, keyword density, and SERP preview.
UTM Code Generator
Create UTM tracking links for Google Analytics: fill in Source/Medium/Campaign... and get a ready-to-copy standard URL.
Meta Tag Generator
Generate SEO meta tags (title, description, keywords, robots, viewport) to paste into your <head>.
Open Graph Generator
Generate Open Graph tags (og:title, og:description, og:image, og:url) for Facebook and Zalo.
Twitter Card Generator
Generate Twitter Card tags (summary, summary_large_image) so your links display nicely on Twitter/X.
Robots.txt Generator
Create a robots.txt file with Allow/Disallow rules, Sitemap declarations, and Crawl-delay for bots.
Sitemap Generator
Generate a sitemap.xml file from a list of URLs, with changefreq, priority, and lastmod set for each URL.
Canonical Tag Generator
Generate rel=canonical tags to standardize URLs and prevent duplicate content.
Hreflang Generator
Generate hreflang tags for multilingual/multi-region websites, including x-default, to avoid duplicate content.
Keyword Density Checker
Check keyword density (1-3 grams) in your content and get warnings for keyword stuffing.
SERP Preview
Preview your Google search result snippet (desktop & mobile) and get warned if your title/description gets truncated.
Robots.txt Tester
Paste your robots.txt and check whether a URL is blocked or allowed for each bot.
Sitemap Validator
Validate your sitemap.xml file: XML syntax and the url, loc, and lastmod tags.
AI & Prompts
Format and optimize prompts, count tokens, validate JSON in AI responses, and strip Markdown.
Prompt Formatter
Clean up and format your AI prompts into a standard structure, right on your device.
Token Counter
Estimate the token count of a prompt for GPT and Claude, right on your device.
JSON Prompt Validator
Validate and format JSON in AI prompts or responses, right on your device.
Markdown Cleaner
Strip Markdown formatting and return plain text, right on your device.
AI Prompt Optimizer
Score your AI prompt and get suggestions to improve it, right on your device.
CSS & UI
Color conversion, color palettes, CSS unit conversion, and other UI utilities.
Color Converter
HEX ↔ RGB ↔ HSL, with a live preview.
PX ↔ REM
Convert CSS units px ⇄ rem/em based on the root font size (default 16px).
Color Palette Generator
Extract the dominant color palette from an image (HEX/RGB/HSL).
CSS Gradient Generator
Create multi-color linear, radial, and conic CSS gradients with a live preview.
Box Shadow Generator
Create multi-layer CSS box-shadow effects with a live preview.
Border Radius Generator
Create CSS border-radius for all four corners and elliptical rounding with a live preview.
Glassmorphism Generator
Create glassmorphism frosted-glass effects using backdrop-filter, with a live preview.
Neumorphism Generator
Create neumorphism (soft UI) effects with soft shadows and a live preview.
Contrast Checker
Check color contrast ratio against WCAG AA/AAA standards.
Tailwind Color Picker
Browse the Tailwind CSS color palette and quickly copy HEX codes or class names.
CSS to Tailwind
Convert CSS into matching Tailwind classes in seconds.
Images
Compress, resize, and convert images, WebP/HEIC, strip EXIF data, OCR, favicons, QR codes, barcodes, and video-to-GIF.
QR Code Generator
Generate a QR code from text or a URL right on your device (no external service calls). Download as PNG.
Image Converter → PNG/JPG
Convert images (WebP, GIF, BMP, AVIF, PNG, JPG...) to PNG or JPG right in your browser.
Image Resizer
Resize images by pixels or percentage, keep the aspect ratio, and download as PNG/JPG.
Image Compressor
Compress images to reduce file size by quality setting or to a target size (KB), and export as JPG/WebP.
Image → WebP
Convert PNG/JPG/GIF to WebP for smaller file sizes, adjust quality, and process multiple images.
Remove EXIF / Location Data from Photos
Strip all metadata (EXIF, GPS/location coordinates, device model) from photos before sharing them. Check whether a photo contains location data.
OCR — Extract Text from Images
Extract text from photos/scans using OCR, with support for Vietnamese and English. Images are processed on your device; the language pack is downloaded only once, on first use.
Measure from Photo
Measure the real-world size of an object from a photo: calibrate using a known reference (2 points) or a 4-corner rectangle (for angled shots, more accurate).
Image to Base64
Convert an image to a Base64 string / Data URI to embed directly in HTML/CSS.
YouTube Thumbnail Downloader
Paste a YouTube link to get the video thumbnail in multiple resolutions, including Max Res, to preview and download.
Favicon / App Icon Generator
Upload one image and generate a full set of standard-size icons for Web (favicon), iOS, and Android. Download individually or all at once.
HEIC → JPG/PNG
Convert HEIC/HEIF photos (iPhone) to JPG or PNG right in your browser, no upload required. Select multiple images.
SVG Optimizer
Optimize and minify SVG files (like SVGO).
Barcode Generator
Generate EAN-13 and Code 128 barcodes and download them as PNG.
Video to GIF
Trim a short video clip into an animated GIF.
Crop Image
Crop an image by selecting the area to keep, then download it as a PNG file.
Rotate & Flip Image
Rotate images 90/180/270 degrees, flip horizontally or vertically, then download as PNG.
SVG → PNG
Convert vector SVG images to PNG with a custom resolution.
View Image EXIF
View an image's EXIF data: camera model, date taken, camera settings, and GPS coordinates.
Security & Encryption
JWT, SHA/MD5 hashing, Base64, AES, bcrypt, password and token generation, all processed locally so secrets never leave your browser.
JWT Decoder
Decode the header and payload of a JSON Web Token. Warns about expiration. Does not verify the signature (offline).
JWT Verify (HS256)
Verify a JWT's HMAC-SHA256 signature using your secret — locally, so the secret never leaves your browser.
JWT Builder (HS256)
Create and sign a JWT with HMAC-SHA256 — handy for generating test tokens. Signing happens locally.
Hash (SHA)
Compute SHA-1/256/384/512 hashes using the Web Crypto API, entirely on your device.
Base64 Encode/Decode
Encode/decode Base64 with full UTF-8 support (works correctly with any language).
Password / Token
Generate strong passwords and secret tokens (API keys, NEWS_INGEST_TOKEN, etc.) using secure crypto — nothing leaves your browser.
MD5 Hash
Compute the MD5 checksum of text (pure JS implementation, since Web Crypto doesn't support MD5).
Text Encryption (AES)
Encrypt/decrypt text using AES-256-GCM with a password (PBKDF2), right on your device.
Bcrypt Hash / Verify
Hash and verify bcrypt ($2a/$2b) passwords right in your browser.
RSA Key Generator
Generate an RSA public/private key pair (PEM) locally using the Web Crypto API.
HMAC Generator
Generate HMAC SHA-1/256/384/512 codes with a secret key using Web Crypto, locally in your browser.
Password Strength
Check your password strength: entropy and estimated crack time — all locally on your device.
Hash Compare
Compare two hashes or verify text against a hash — safely, right on your device.
CRC32 Checksum
Calculate a CRC32 checksum (in hex and decimal) right on your device.
Network & DNS
DNS, WHOIS, IP/GeoIP lookup, HTTP client, User-Agent parser; some tools require an internet connection (clearly noted on the page).
IP / CIDR Calculator
Calculate an IPv4 subnet from CIDR: network, broadcast, host range, netmask, and host count.
User-Agent Parser
Parse a User-Agent string to identify the operating system, browser, and device.
DNS Lookup
Look up DNS records (A, AAAA, MX, TXT, CNAME, NS...) via DNS-over-HTTPS.
WHOIS Lookup
Look up domain and IP registration info via RDAP.
What Is My IP
See your public IP address along with its location (GeoIP).
API Tester
Send HTTP requests (GET/POST/PUT...) like a mini Postman.
Reverse DNS
Look up the reverse domain (PTR record) for an IP address via DNS-over-HTTPS.
Text
Word count, case conversion, slug generator, Lorem Ipsum, line sorting/deduplication, and URL/HTML entity encoding.
Case Converter
camelCase, snake_case, kebab, CONSTANT, Title Case, PascalCase…
URL Encode/Decode & Parser
Encode/decode URLs and parse query strings into a table.
Lorem Ipsum
Generate Lorem Ipsum placeholder text by paragraph or sentence count for design mockups.
Word & Character Counter
Count characters, words, sentences, paragraphs, and lines, plus estimated reading time — updates live as you type.
Slug Generator
Convert a title into a URL slug: strip accents, lowercase, and join words with hyphens.
Line Tools
Sort, deduplicate, reverse, trim, remove blank lines, shuffle — process line-based lists.
HTML Encode/Decode
Encode/decode HTML entities (& < ...). Prevents XSS when embedding text into HTML.
Hashtag Generator
Enter a keyword and get ~30 suggested hashtags for TikTok, Instagram, and Facebook. Copy with one tap.
Reverse Text
Reverse text by character, by word, or by line order.
Random Text Generator
Generate random text, character strings, and numbers with a custom length and count.
Merge, split, and rotate PDFs; convert PDF to/from images; images to PDF; Word to/from PDF.
PDF to Image
Split each PDF page into a PNG/JPG image, choose the resolution, and download individual pages or all of them. No upload required.
Merge / Split / Rotate PDF
Merge multiple PDFs into one, split or delete pages by range, and rotate pages. 100% on your device, no upload.
Merge Images to PDF
Combine multiple images or camera captures into a single PDF file: document scan filters, drag-and-drop reordering, A4/Letter paper size, and file compression.
Word → PDF
Convert a Word file (.docx) to PDF right in your browser, no uploads needed.
PDF → Word
Extract text from a PDF into a Word file (.doc). Text only — layout is not preserved.
Business & Finance
Pricing and profit margin, VAT, installment loans, compound interest, gross-to-net salary, exchange rates, crypto prices, and investing.
Selling Price & Profit
Calculate selling price from cost price using markup or margin, or analyze profit when you know both the cost and selling price.
Discount / Markdown
Calculate the price after a percentage discount and the amount saved, or work out the discount % from the original and final price.
VAT Calculator
Add VAT to an amount or extract it (8%/10%): get the tax amount and the total/pre-tax price.
Installment / Loan Interest
Calculate the monthly payment, total interest, total amount due, and repayment (annuity) schedule for a loan or installment plan.
Compound Interest / Savings
Calculate the future value of savings or investments with recurring contributions, compounded over time.
Gross to Net Salary
Convert between Gross and Net salary based on Vietnam's mandatory social/health/unemployment insurance (BHXH/BHYT/BHTN) and progressive personal income tax.
Break-even Point
Calculate the break-even quantity and revenue from fixed costs, selling price, and variable cost per unit.
Bill Split & Tip
Split a bill evenly among several people, add a tip percentage, and get the amount each person owes.
Percentage Calculator
X% of Y, what percent X is of Y, and the percentage change from A to B.
Foreign Exchange Rate
Convert and check exchange rates for ~160 currencies (USD, EUR, JPY, VND...) using live, up-to-date rates.
Live Crypto Prices
Check Bitcoin, Ethereum, and other prices in USD/VND with 24h change, and calculate profit/loss on your position. Data from CoinGecko.
Investment Calculator
Trade profit/loss (including fees), average cost basis (DCA), position sizing by % risk, and risk:reward ratio. For stocks and crypto.
Invoice Generator
Create invoices with your details, line items, and taxes, then print or save them as a PDF.
Health & Lifestyle
BMI & TDEE, age calculator, lucky wheel spinner, Pomodoro timer, and stopwatch.
BMI & TDEE Calculator
Calculate BMI, BMR, and TDEE (daily calorie needs) from your height, weight, age, and activity level.
Age Calculator
Enter your birth date to get your exact age in years/months/days, total days and hours lived, and a countdown to your next birthday.
Lucky Spin Wheel
Enter a list of names or prizes and spin the wheel for a fair random pick. Great for raffles, mini-games, and dividing tasks.
Pomodoro Timer
A Pomodoro timer for focused work sessions and breaks.
Stopwatch & Countdown
A stopwatch and countdown timer.