Developer tools
Every tool here is a static page that runs in your browser. What you paste never leaves it — no upload, no server round trip, no account — so you can use a real production value rather than a redacted one. Each tool ships with reference guides whose claims are checked by running the code.
Available now
- UUID GeneratorGenerate and decode UUID v1, v3, v4, v5 and v7 — in bulk, entirely in your browser.Generate & decode UUIDs →
- JSON FormatterFormat, validate and inspect JSON — with the precision traps that silently corrupt large numbers.Format & validate JSON →
- Base64 EncoderEncode and decode Base64 and base64url, with correct padding and UTF-8 handling.Encode & decode Base64 →
- JWT DecoderDecode a JWT and read its claims — and understand why decoding is not verifying.Decode & inspect JWTs →
- Cron ExpressionBuild and read cron expressions, with the next run times and the day-of-week traps spelled out.Build & explain cron →
How these are built
- Nothing is uploaded
- Parsing, generating and decoding all happen in your browser, so a production identifier or a real token never reaches a server. The pages keep working offline once loaded.
- Claims are executed, not asserted
- The guides run their own code before publishing and quote the real output. That has repeatedly changed what we wrote — including refuting two widely repeated beliefs that did not hold when measured.
- Sources are primary
- Guides cite the RFC, the language reference or the vendor documentation rather than other blog posts, and say plainly when something could not be verified in the environment at hand.