What LanguageTool Actually Is (From Someone Who Proofreads For A Living)
I run a small English editing and proofreading side business for ESL founders, and I have spent the last two years living inside grammar checkers. LanguageTool is the one I actually pay for. It is a German-built tool (Potsdam, LanguageTooler GmbH) that checks grammar, spelling, punctuation and style across 30-plus languages, on top of an open-source engine that has been running since 2003. The basic experience: type or paste text, it underlines problems in colour - red for spelling, yellow for grammar, blue for style - and most of the time it tells you why, not just what.
Three things separate it from the rest of the category. First, the language coverage. It genuinely handles German, French, Spanish, Dutch, Portuguese and Polish close to native level, including regional variants like British versus American English and Swiss versus Austrian German. If your client base writes in anything other than English, most checkers are useless to you and this one is not. Second, the core engine is open source under GNU LGPL. You can run the whole thing on your own server, which means no text ever leaves the building - that single fact wins you clients no cloud-only tool can even pitch to. Third, it is cheap. Premium runs about $5.83 a month on annual billing, roughly half of Grammarly's $12, and the free tier is not a teaser: core grammar and spelling checks work with no account and no card.
Pricing in full. Free gives you the core checks with a per-check character cap (roughly 2,000-10,000 characters depending on where you paste) and about three AI paraphrases a day. Premium is $24.90 month-to-month, $69.90 a year (about $5.83/mo), or about $4.17/mo on the two-year plan - it raises the cap to 150,000 characters per check, adds unlimited AI paraphrasing, the stricter Picky Mode style rules, a custom style guide, and 20,000-plus additional checks for English, German, French, Spanish, Dutch, Polish and Portuguese. Teams runs about $6.99 per user a month and adds a shared style guide, a team dictionary and member management. There is also a developer API and a self-hostable server, both free under the open-source licence. It runs as a browser extension (Chrome, Firefox, Edge, Safari), inside Word and Google Docs, as a desktop app for Windows, macOS and Linux, and LibreOffice has shipped with LanguageTool support for years.
Why It Pays (The Real Income Angle)
Here is the part that matters: the tool is free or nearly free, and the people who need it are everywhere. Non-native speakers are the global majority of business English writers, and they pay real money to not sound like it. Six ways I have seen solo operators bill for this:
1. English proofreading for ESL founders and teams. This is the core gig. A German startup founder writing investor updates, a Japanese agency writing client reports, a Brazilian e-commerce team writing product pages - they all pay $30-150 per document to have a human (plus LanguageTool) make it clean. At ten documents a month that is $1.5K-3K against a $0-5 tool bill. The margin is the invoice minus an hour of your time.
2. Multilingual content QA for cross-border teams. Here is where LanguageTool beats every English-only checker. Teams publishing in French, Spanish, German and English pay $200-800 a month for someone to run their output through LanguageTool in each language, fix the errors and return a clean pass. Most freelancers cannot do this because they only own one language; if you own two or three, you have pricing power nobody else in your market has.
3. Academic and admissions editing. Students and researchers writing papers, theses and grad-school applications pay $50-200 per piece, and the demand never stops. LanguageTool's Picky Mode is built for exactly this - stricter formal style rules, passive-voice flags, wordiness - and the browser extension means you can check a Google Doc the same way you check an email.
4. Self-hosted deployment for privacy-sensitive organisations. Law firms, clinics, government contractors and European mid-caps have strict data-residency rules: their text cannot go to a US cloud. LanguageTool is the only mainstream grammar checker you can install on their server. A typical engagement is $1K-5K to set it up (Docker, a VM, reverse proxy, user accounts) plus $200-500 a month to maintain and update it. I have seen freelancers run three of these retainers at once - it is the highest-margin, lowest-competition work in this category.
5. API integration into publishing workflows. Marketing agencies and software teams want every blog post and help article checked before it ships. Build a small pipeline (a CMS hook or a CI step) that pushes drafts through the LanguageTool API and emails a report. Charge $500-2K per integration. The API itself costs nothing to start with; you bill for the plumbing.
6. Style-guide and voice consistency retainers. Content teams with six writers all using different terminology pay $300-1K to set up a shared style guide and team dictionary, then $150-400 a month to maintain it. LanguageTool enforces the rules mechanically, which is exactly what a content manager is buying when they say "everyone keeps spelling the product name differently."
The math that sells the service: a client paying $80 for a cleaned document is not buying a $5 subscription, they are buying "my English no longer embarrasses me in front of investors." That gap is the product, and the tool just makes the gap easy to deliver.
How I Actually Run It (A Real Workflow)
For a typical 2,500-word investor update from a German founder: I run it through LanguageTool first (the free tier handles it in one paste), fix the mechanical errors it flags - comma rules, article mistakes, word order, false friends like "actual" versus "aktuell" - then read it once myself for the tone and flow issues a rule-based checker cannot see, like a sentence that is technically correct but sounds stiff. Total hands-on time is 30-40 minutes. I bill $90. The Premium subscription is invisible inside the invoice.
One honest note from experience: LanguageTool catches maybe 70-80% of what a careful human editor catches on English text. The last 20% is your judgement. That is not a bug - it is why the client pays you instead of just running their own text through the free checker. Clients can install the same tool; what they cannot buy is the judgement pass. So never sell yourself as "LanguageTool with a human attached." Sell the judgement.
What LanguageTool Is Bad At (Honest)
- English suggestions are less polished than Grammarly's. No tone detection, no full-document rewrite, and some style suggestions read like they were written by a linguist's rulebook, not a copywriter. For pure English-only users who want maximum polish, Grammarly is still the better product.
- The free per-check character cap is annoying. Long documents have to be pasted in chunks. It is workable, but it is friction you have to manage, and it pushes casual users toward the paid plan faster than they want.
- The AI paraphrasing is mediocre. Premium's unlimited rewrite is fine for flattening one awkward sentence, but it will occasionally hand you something grammatically correct and clearly worse. Treat it as a suggestion, never a final pass.
- Pricing punishes month-to-month. $24.90 a month is steep for what it is; the sane prices ($4.99-5.83/mo) only exist on annual or two-year billing. If you cannot commit, the free tier is honestly fine for most single documents.
- Self-hosting is not for non-technical people. The open-source server is genuinely free, but you need Docker, a VM, TLS and someone to keep it updated. It is a service you sell to organisations, not something a normal client does themselves.
- Advanced style checks thin out outside the main languages. Picky Mode and the extra 20,000 checks are strong for English, German, French, Spanish, Dutch, Polish and Portuguese - but the deeper you go into smaller languages, the thinner the rules get.
LanguageTool vs The Alternatives
| Tool | Best at | Language coverage | Self-host / API | Price (annual) |
|---|---|---|---|---|
| LanguageTool | Multilingual grammar, privacy, value | 30+ languages, regional variants | Yes - open source + API | ~$5.83/mo |
| Grammarly | English polish, tone detection | English mainly | No - cloud only | ~$12/mo |
| ProWritingAid | Deep writing reports (readability, repetition) | English mainly | No | ~$10/mo |
| QuillBot | Rewriting, summarizing | English mainly | No | ~$9.95/mo |
| Sapling | Customer-service and sales message QA, API-first | English mainly | API only | ~$25/mo |
The honest summary: Grammarly wins on pure English finesse, QuillBot wins if your need is rewriting rather than checking, and LanguageTool wins the moment you go multilingual, privacy-sensitive or price-conscious - or all three.
Who Should Use It (And Who Shouldn't)
Use it if: you edit or proofread for ESL clients and want one tool that covers their native languages too; you work with cross-border teams publishing in several languages; your clients are privacy-sensitive (law, clinic, EU mid-cap) and need self-hosting; you are an independent author who wants 90% of the checking value for half the Grammarly price; or you are a freelancer looking for a service to sell, because the demand pool here is enormous and the tool cost is near zero.
Skip it if: you only write English and want the absolute best English suggestions money can buy (Grammarly); your main need is rewriting and summarizing rather than checking (QuillBot); or you have no tolerance for pasting long documents in chunks and refuse to pay for Premium.
Getting Started (6 Tips)
- Install the browser extension first - it checks every field you type in, from Gmail to Notion, and that is where you will feel the value fastest.
- Run one real client document through the free tier before buying anything. If the per-check cap drives you mad, then buy Premium; most single documents fit fine.
- Read the explanation under every suggestion. LanguageTool tells you why - click the underline - and that is the difference between learning and blind clicking.
- Set up a personal dictionary and style guide on day two. Brand names, technical terms and your client's preferred spellings stop being flagged, and your style guide enforces the same voice across documents.
- If you sell editing services, use Picky Mode for formal and academic work. It catches wordiness and passive voice that the normal mode lets through - exactly what thesis and investor-update clients pay for.
- Paste long pieces into the standalone web editor rather than fighting the extension's per-check cap - it is the same engine, just more room to work.
The bottom line: LanguageTool is not the flashiest grammar checker, and it will not rewrite your English into something award-winning. But for anyone whose clients write in more than one language, or whose clients cannot send text to a US cloud, it is the only tool in the category that works at all - and for a solo editor it is the cheapest way I have found to turn "please check my English" into a monthly invoice.