Free Developer Tools
JSON, Base64, JWT, regex, hashes, colours and format converters.
JSON Formatter
Pretty-print, validate and minify JSON with clear error positions.Base64 Encoder / Decoder
Encode and decode Base64 and Base64URL with UTF-8 support.URL Encoder / Decoder
Percent-encode or decode URLs, with a query-parameter table.JWT Decoder
Read a JWT’s header, payload and expiry — privately.Regex Tester
Test regex live: matches, groups, flags and replace.Color Converter
HEX, RGB, HSL, HSV and CMYK, with a WCAG contrast check.Hash Generator
MD5 and SHA hashes of any text, computed in your browser.UUID Generator
Generate v4 or v7 UUIDs in bulk with secure randomness.CSV to JSON Converter
CSV ↔ JSON with delimiter detection and quoted fields.YAML to JSON Converter
YAML ↔ JSON for config files, with clear errors.Markdown to HTML
Markdown to HTML with tables and a safe live preview.Cron Expression Explainer
Cron schedules explained in plain English, with next run times.HTML Entity Encoder
Escape and unescape HTML entities like & and é.
Developer tools that keep your data private
Many online developer utilities send what you paste to a server. These don’t: formatting, encoding, decoding and hashing all happen in your browser, so you can safely work with API responses, tokens and configuration files.
- Data formats: JSON formatter and validator with exact error positions, CSV ↔ JSON, YAML ↔ JSON and Markdown to HTML with a sandboxed preview.
- Encoding: Base64 and Base64URL, URL percent-encoding and HTML entities, all UTF-8 safe.
- Security and IDs: a JWT decoder, a hash generator for MD5 and SHA-2, and a UUID generator for v4 and time-ordered v7 IDs.
- Everyday helpers: a regex tester with named groups and replacements, a colour converter with WCAG contrast, and a cron expression explainer that shows the next run times.
Each tool page explains the format or standard it follows, with examples you can copy. Bookmark the ones you use most so they are one click away.