Work · Case study

Corrector Català

Your language. Your words. Your data.

Digital productChrome extensionOpen sourcePrivacy 2026

An editorial typographic composition presenting Corrector Català through its original mark, red colour and wavy underline.

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The starting point

In January 2025 the official LanguageTool extension went Premium-only: a fourteen-day trial and then, unless you pay, the underlines disappear. For millions of people it was an annoyance. For anyone writing in Catalan it meant losing the only decent checker they had in the browser.

The engine, however, is still free software (LGPL) and the Catalan rules — more than 2,500 of them, maintained by Softcatalà and the community — are excellent. All that was missing was putting the pieces back together in a way that does not depend on anyone’s bottom line.

What we built

Our own server, or whichever one you choose. We expose the free LanguageTool engine on a server self-hosted at the studio, with a compatible API (v2/check) and a limit of 30 requests per minute per IP. If you would rather run your own, Docker and nginx get you there in five minutes: the documentation is in the repository.

A brand-new Chrome MV3 extension, free forever. It underlines errors in text areas, search boxes, comments and web editors (Gmail, Reddit, X, WhatsApp Web) on Chrome, Edge, Brave and Vivaldi. Synced personal dictionary and domain list; automatic dark mode.

Four variants with automatic detection. Standard Catalan, Valencian, Balearic and Spanish. Many Catalans write in two languages over the course of a day: the extension detects it from the text and checks in the right variant, with manual selection whenever needed.

Privacy you can verify. No analytics, no cookies, no trackers. Text travels over HTTPS only to the server you have chosen in the options. And because the code is open (AGPLv3), anyone can audit it.

A landing page with a live demo. Paste a text, review the suggestions and accept the corrections you need. The case recording shows actual engine responses and a second check of the corrected text. In the September 2026 review, the website offers manual installation for Chrome and the repository still lists the Firefox build as pending.

The design decision

Correcting where you already write.

The value is not in replacing one extension. It is in letting the person writing choose the server, understand where their text goes and keep an alternative even when a third party changes its business model. A basic tool for a language should not be able to vanish with a pricing change.

The project in numbers

language variants with automatic detection

trackers, cookies and accounts

+2,500

Catalan rules in the free engine

How it works · and why it matters

A text’s journey is short and can be drawn in full. A content script reads what you type, a service worker batches it and sends it over HTTPS to the LanguageTool server you chose, and the suggestions come back into the same text box. There is no other destination: no analytics, no third parties, no copies.

Where your text travels · and where it does not

Compared with the official extension, the difference is not features but terms: free with no expiry date, open source and a server of your choosing. Compared with Softcatalà’s web checker — same engine, and excellent — the advantage is checking right where you write, with no copy and paste.

Three ways to check Catalan in 2026

	Corrector Català	LanguageTool (official extension)	Softcatalà (web checker)
Price	Free and libre (AGPLv3)	Limited free tier; full checking is Premium	Free
Checks as you type, on any website	Yes	YesPremium needed to see every error	NoYou paste the text into the website
Catalan variants	YesStandard, Valencian and Balearic, auto-detected	Yes	YesStandard, Valencian and Balearic
Spanish	YesAuto-detected	Yes30+ languages	No
Own server (self-hostable)	YesDocker + nginx, in 5 minutes	No	No
Analytics and trackers	YesNone: the text only goes to the server you choose	PartlyUser account and cloud service	PartlyThird-party web service
Open source	YesExtension and server, AGPLv3	PartlyLGPL engine; proprietary extension	PartlyLGPL engine
Browsers	Chrome, Edge, Brave, Vivaldi · Firefox in progress	Chrome, Edge, Firefox, Safari, Opera	Any (it is a website)
LanguageTool-compatible API	Yesv2/check · 30 requests/min per IP	PartlyPaid for heavy use	No
Synced personal dictionary	Yes	YesWith an account	No

Data from each service's public pages as of 3 September 2026. Softcatalà also links to the official LanguageTool extensions.

And the honest part: it is a small project. Since May 2026 a few dozen people use it, the Chrome Web Store listing is still under review and manual installation puts some people off. We did not build it to win market share. We built it so that it exists. If LanguageTool goes free again tomorrow, great: there will be two.

How it went

01The lossJanuary 2025: full checking moves behind Premium

02The engineLGPL LanguageTool and Softcatalà rules, on our own server

03The extensionChrome MV3, four variants, zero tracking

04The open releaseCode, deployment and documentation under AGPLv3

05May 2026First corrections in production; Web Store and Firefox on the way

Gallery · the project in pictures (click to enlarge)

Write, review, continue.

Write a text
Review each suggestion
Check the result

An actual recording of the web checker, captured on 24 September 2026 using a sample text without personal data. The engine detects two errors; its suggestions are accepted and the text is checked again.

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More images from the project 8 ↗