Developer Tools
JSON, encoders, hashes, regex, and code utilities.
Free online developer tools that run entirely in your browser. Format and validate JSON, encode and decode Base64, generate UUIDs and hashes, test regex, and convert timestamps — all without sending a single byte to a server. Perfect for quick debugging, CI scripts, or working with sensitive data like API keys and JWT payloads.
When to use these tools
Start with the format you are working in. If you have raw JSON, the JSON Formatter will validate it and point at the exact line that breaks parsing — useful when a production API response 500s and you are reading the payload by eye. If the data has crossed a config boundary, JWT Decoder and Base64 Encoder & Decoder handle the two encodings you meet most often; both decode locally, so tokens and credentials never touch a server. Regex Tester is the tool to reach for when a pattern works in one language and not another: it flags the differences in escape handling and capture-group numbering that cause most of those failures. For anything you paste into a test fixture or a local script, UUID Generator and Hash Generator cover the common needs without a terminal. The one caveat worth stating plainly: these tools help you inspect and transform data, they do not validate that your schema is correct in production.
Showing 23 of 23 developer tools
JSON Formatter
Format, validate, and minify JSON with inline error reporting.
JSON ↔ YAML Converter
Convert between JSON and YAML formats bidirectionally.
XML Formatter
Pretty-print and minify XML with validation.
Base64 Encoder / Decoder
Encode text to Base64 or decode Base64 to text with UTF-8 support.
UUID Generator
Generate RFC 4122 v4 UUIDs in bulk using the Web Crypto API.
Hash Generator
Generate SHA-1, SHA-256, SHA-384, SHA-512 hashes via Web Crypto.
HMAC Generator
Generate HMAC signatures (SHA-256/384/512) for a message and secret.
JWT Decoder
Decode and inspect JSON Web Token header and payload.
JWT Generator
Generate signed JSON Web Tokens (HS256) with custom claims.
Regex Tester
Test regular expressions with live match highlighting and flags.
URL Encoder / Decoder
Encode or decode URL components and full URLs.
Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates.
Color Converter
Convert colors between HEX, RGB, HSL with a live preview.
HTML Entity Encoder
Encode or decode HTML entities in text.
SQL Formatter
Pretty-print and format SQL queries with keyword casing.
Markdown to HTML
Convert markdown to raw HTML source for emails and static sites.
Text Diff
Compare text at line, word, or character level with unified diff output.
Cron Expression Generator
Build cron schedules visually and preview next run times.
Diff Checker
Compare two texts line-by-line with a color-coded LCS diff.
Markdown Preview
Write Markdown and see a live rendered HTML preview.
CSS Minifier
Minify CSS by removing comments, whitespace, and empty rules.
JS Minifier
Minify JavaScript by removing comments and unnecessary whitespace.
HTML Minifier
Minify HTML by removing comments, whitespace, and empty attributes.
Guides & tutorials
Learn the best practices behind these developer tools.
UTM Parameters Explained: Track Campaigns Without Breaking Analytics
How to build UTM tracking URLs the right way: utm_source vs utm_medium vs utm_campaign, naming conventions that keep reports clean, encoding mistakes to avoid, and QR-code tracking.
4 min read·Read guidePassword Entropy Explained: The Math Behind Truly Strong Passwords
What password entropy actually measures, the length × character-pool formula, crack-time tables with honest assumptions, why human passwords fall short, and the NIST rules that follow from the math.
5 min read·Read guideUnix Timestamps Explained: UTC, Timezones & Common Pitfalls
What a Unix timestamp really is, why the epoch starts in 1970, how to convert timestamps to dates (and back) correctly, and the timezone and 2038 bugs that catch everyone out.
4 min read·Read guide