Developer Tools
Fifteen free tools for developers, built the way developers like them: fast, private and honest about their limits. Format and validate JSON, encode and decode Base64, test a regular expression against live text, generate a UUID v4, hash text with MD5 or SHA-256, encode a URL, decode a JWT header and payload, convert a Unix timestamp, pick a colour and check its contrast, convert decimal, hex, binary and octal, or turn JSON into CSV and back.
Everything runs in your browser — your code, tokens and test data are never uploaded. That is a deliberate choice: the JWT decoder, for example, decodes only and never verifies a signature, and the tools warn you never to paste production secrets into any online tool, including this one. Use test data wherever you can.
JSON Formatter
Format, minify and validate JSON, with clear error messages.
Format →Base64 Encoder
Encode and decode Base64 with correct UTF-8 handling.
Encode →Regex Tester
Test regular expressions live, with highlighted matches.
Test →UUID Generator
Random UUID v4, one or ten at a time, with or without hyphens.
Generate →MD5 & SHA-256 Hash Generator
Hash any text with MD5 and SHA-256 in your browser.
Hash →URL Encoder
Encode and decode URLs and URL components safely.
Encode →JWT Decoder
Decode a JWT header and payload. Decodes only — does not verify.
Decode →Unix Timestamp Converter
Convert epoch timestamps to dates and dates to timestamps.
Convert →Color Picker
HEX to RGB and HSL, with WCAG contrast checks.
Pick →Decimal to Hex Converter
Decimal, hex, binary and octal — one input updates all four.
Convert →JSON to CSV Converter
Turn a JSON array into CSV, and CSV back into JSON.
Convert →Cron Explainer
Explain a cron expression and show next run times.
Explain →Markdown Editor
Write Markdown, preview HTML, export to PDF.
Edit →Colour Palette Generator
Extract a colour palette from any image.
Extract →File Hash Checker
Get SHA-256, SHA-1 and MD5 hashes of any file.
Check →Browse Other Categories
- Finance Calculators — mortgage, salary, loans, retirement and more.
- Health Calculators — BMI, calories, body fat, due date and tips.
- Math & Date Calculators — scientific, fractions, averages, age and time zones.
- Text Tools — word counter, case converter, readability and more.
- Generators — passwords, QR codes, barcodes and SEO generators.
- File Tools — merge PDFs, convert images, compress files — all in your browser.