Developer tools
14 free developer tools · Encode, format, generate
The small utilities you reach for several times a day and would rather not paste into an unknown server: formatting a JSON payload, decoding a token to see why it was rejected, checking a regular expression, or generating an identifier. Tokens and payloads routinely contain credentials, which is the argument for running these locally.
All developer tools
- JSON formatter & validator Beautify, minify and validate JSON with error locations.
- JWT decoder Decode a JWT and inspect its claims and expiry.
- Base64 encode & decode Encode or decode Base64, including URL-safe variants.
- Regex tester Test a regular expression with live match highlighting.
- Password generator Cryptographically random passwords with a strength readout.
- URL encode & decode Percent-encode or decode URLs, and inspect the parts.
- HTML entity encode & decode Escape HTML special characters, or decode entities back.
- JSON to CSV converter Convert between JSON arrays and CSV, both directions.
- UUID generator Generate random v4 or time-ordered v7 UUIDs in bulk.
- Hash generator MD5, SHA-1, SHA-256, SHA-384, SHA-512 and CRC32 at once.
- Color converter Convert HEX, RGB, HSL and HSV, with WCAG contrast checks.
- Cron expression generator Explain a cron expression and see its next run times.
- QR code generator Make QR codes for links, Wi-Fi, email or contacts.
- Unix timestamp converter Epoch to date and back, with the unit auto-detected.
Guides
- Base64 is not encryption (encoding, encryption and hashing, untangled) Encoding, encryption and hashing all turn data into gibberish — and solve completely different problems. What each guarantees, and where each is misused.
- How to read a JWT (and what the three parts actually do) A JSON Web Token is three Base64 sections split by dots — readable by anyone, forgeable by no one. How the format works, the claims, and the classic pitfalls.
- Cron syntax explained: reading the five fields without a cheat sheet Cron expressions like 0 3 * * 1 pack a schedule into five fields. How to read them, the day-of-month vs day-of-week trap, and the mistake that fires 60 times.
- What checksums are for: verifying a download with a hash Sites publish SHA-256 hashes next to downloads for a reason. What a checksum proves, what it cannot prove, how to check one on any OS, and why MD5 still exists.