LocalFirstTools

LocalFirstTools is a set of 28 free developer utilities that run entirely in your browser. You can format and validate JSON, convert JSON to YAML, CSV, XML or TypeScript, format XML, SQL and HTML, view 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. Every tool works the same way: you paste or drop your data, your browser does the processing, and you copy the result. There's no upload endpoint, no account, no ads and no analytics event that carries your input. That matters when you're pasting a production API response, a bearer token or a customer export. You don't have to take that on trust. Each page has the same 10-second check: open DevTools → Network, clear it, run the tool again and see that no new requests show up. Or go offline and keep using the tool you already loaded. Each build publishes a manifest and SHA-256 checksums of its HTML and scripts. Each tool also says what it doesn't do. For example, the JWT decoder decodes but doesn't verify signatures. LocalFirstTools is built by Patrick, a developer in the Netherlands.