LocalFirstTools

LocalFirstTools is a set of 28 free developer utilities that run entirely in your browser tab. Format and validate JSON, XML, SQL and HTML, open large CSV files, decode JWTs, encode and decode Base64, URL and hex, generate SHA-256/MD5 hashes, UUID v4/v7 and passwords, convert Unix timestamps, test regexes, diff text and explain cron expressions.

There is no upload endpoint, no account and no ads, which matters when you paste a production API response, a bearer token or a customer export. You can verify it yourself: open DevTools, clear the Network tab, run a tool again and see that no new requests appear, or go offline and keep using the loaded tool. Each build publishes SHA-256 checksums. Built by Patrick, a developer in the Netherlands.