DevTools
The tools you open twenty times a day, on one site.
Format a JSON, decode a JWT, validate an IBAN, work out the VAT on an invoice or read a cron. It all runs in your browser: what you paste never leaves your machine and there is no account.
- Last release
- v2.1.0, Sep 27, 2026
- Web
- devtools.alvarotc.com
- Tools
- 52 in eight groups
- Languages
- Spanish and English
- Accounts
- No accounts, no server
- Themes
- Light, dark and terminal
Screenshots
Screens from v2.1.0 on desktop.
Formatted JSON A valid JWT IBAN broken down A freelancer invoice
Tools
Fifty-two, in eight groups. Each has its own page in Spanish and English.
UUID, ULID & NanoID
UUID v4 and v7, ULID and NanoID in bulk, plus a validator that tells you the version.
What it does
What all 52 share.
Nothing leaves the browser
There is no backend. A JWT, an IBAN or a file to hash is processed on your machine.
Three themes
Light, the default; dark, in graphite; and terminal, green phosphor on black.
Seeded test data
UUIDs, cards, shuffled lists or a thousand fake people. The same seed gives the same output.
- Keyboard shortcutsCtrl K or / to search, ? for help, c to copy the result and 1 to 9 to switch tabs.
- Remembers only what is safeYour JSON or regex is still there when you come back. A DNI, IBAN, card or JWT never is.
- Spanish formats built inDNI and NIE, CIF, IBAN, plates, Social Security, VAT, IRPF and business days with holidays.
- Favorites and recentsIn the sidebar and on the home page, so the usual ones are one click away.
Why it exists
It started in February as fourteen utilities in a SPA, so I could stop pasting tokens into sites I did not know.
In September I rebuilt it in Astro and Svelte and it grew to 52: the ones I open every day, plus the ones you need to work in Spain, like DNI, IBAN, VAT or IRPF withholding, which I never found in one place.
How it is built
- Astro 7 with Svelte 5 islands: each tool is a static page that only hydrates its component.
- Each tool keeps its logic in plain TypeScript, with no DOM, tested with Vitest.
- Browser tests with Playwright for every tool.
- Pages in Spanish and English, each with its own URL, title and search description.
- MIT license, code at github.com/alvarotorresc/devtools.
Changelog
- v2.1.0, Sep 27, 2026Thirty-eight new tools in three batches: identifiers, converters, calculators, random and reference. From 14 to 52.
- v2.0.0, Sep 26, 2026The old SPA rebuilt in Astro and Svelte: three themes, Spanish and English with their own URLs, and the 14 tools improved.