Tools
Free developer tools
Small utilities for the jobs that come up between systems \u2014 formatting a payload, decoding a token, explaining a cron expression, checking a contrast ratio. Every one runs entirely in your browser.
Everything runs on your device. These tools make no network requests and have no server component — whatever you paste in stays in your browser, which is both the fastest possible architecture and the reason it is safe to decode a real token or format a real config file here.
24 tools
Encoding & conversion
Encoding & conversion
Take data in one shape and get it back in another — formatting, encoding, and converting between the formats that show up between systems.
JSON Formatter
Pretty-print and validate JSON, with precise error positions.
Base64 Encoder / Decoder
Convert text to and from Base64, with URL-safe support.
URL Encoder / Decoder
Percent-encode or decode URLs, with a query-string breakdown.
JWT Decoder
Read a JWT's header, claims and expiry without sending it anywhere.
YAML ↔ JSON Converter
Convert between YAML and JSON in either direction.
CSV ↔ JSON Converter
Turn CSV rows into JSON objects, or flatten JSON back to CSV.
Case Converter
Convert identifiers between camel, snake, kebab, Pascal and more.
Markdown Previewer
Write Markdown, see rendered output and HTML side by side.
Generators
Generators
Produce identifiers, credentials, codes and placeholder content, using your browser's own cryptographic random source where randomness matters.
UUID Generator
Generate v4 or time-sortable v7 UUIDs in bulk.
Password Generator
Generate strong random passwords or memorable passphrases.
Hash Generator
Hash text with MD5, SHA-1, SHA-256, SHA-384 or SHA-512.
QR Code Generator
Create styled QR codes with your own logo, and download as PNG or SVG.
Lorem Ipsum Generator
Generate placeholder paragraphs, sentences or words.
Slug Generator
Turn titles into clean, URL-safe slugs.
Favicon Generator
Upload an image, get every favicon size plus the HTML to use them.
Calculators & testers
Calculators & testers
Evaluate, explain and compare — test a pattern, read a schedule, check a contrast ratio, or find what changed between two files.
Regex Generator
Turn example values into a working pattern, and see why it works.
Regex Tester
Test patterns with live highlighting and capture group inspection.
Cron Parser
Explain any cron expression and preview its next run times.
Timestamp Converter
Convert Unix epoch timestamps to dates and back.
Color Converter
Convert between HEX, RGB and HSL with a live preview.
CSS Gradient Generator
Build linear, radial or conic gradients and copy the CSS.
Text Diff Checker
Compare two texts side by side and see exactly what changed.
Word Counter
Count words, characters and sentences with reading time.
SEO
SEO
Check how a page presents itself before you publish it, rather than after someone shares it.