I got tired of ad-covered, sign-up-walled utility sites, so I spent the last few weeks building my own toolbox: 79 free developer tools at https://devtoolbelt-tools.vercel.app/
A few I actually use myself:
- UULE Generator (https://devtoolbelt-tools.vercel.app/tools/uule-generator) — generate Google's location parameter to simulate local search from any city. I verified the protobuf encoding byte-for-byte against published test vectors.
- UUID v4 + v7 (https://devtoolbelt-tools.vercel.app/tools/uuid-generator) — bulk generation, time-ordered v7 per RFC 9562.
- JSON to CSV (https://devtoolbelt-tools.vercel.app/tools/json-to-csv) — nested objects flattened, RFC 4180 quoting.
- Extract Regex Matches (https://devtoolbelt-tools.vercel.app/tools/extract-regex-matches-from-text) — with capture groups, presets for emails/URLs/numbers.
- Google SERP Preview (https://devtoolbelt-tools.vercel.app/tools/serp-preview) — pixel-width meter (600px title), desktop/mobile views.
Plus the usual suspects: Base64/URL/HTML/hex/binary encoders, Morse code, ROT13/47, case converters, word counters, password generator, test credit card numbers (Luhn-valid, test-only), and more.
How it's built:
- Astro, fully static. Every tool is the same 6-file pattern: pure
logic.ts+logic.test.ts+ UI. - ~2,300 Vitest tests. Logic never touches the DOM, so everything is unit-tested.
- Anything that can run client-side does — most tools never send your input to a server. Nothing is stored.
- Each page ships SEO meta + FAQ schema.
What I'm figuring out now: which tools deserve to exist. Search Console says my Google Search URL generator and 2FA tool get the most impressions, so I'm doubling down on the search/dev cluster next.
What small utility do you wish existed? Genuinely taking requests — if it's a pure function, I can usually ship it the same day.
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