Grammar checkers fix your text.
MistakeMate trains you.
The Chrome extension checks your writing on your device — your words never leave it. The mistakes you actually make become a few minutes of daily practice, until they stop coming back.
Corrections are free, forever. The learning plan is $9/month billed annually ($15 month to month).
Checking happens on your device. Your text never leaves it.
Can we still ship by Friday?
depends on — “depend” takes “on”, not “of”
Fixed. Most tools stop here.
Making this one yours…
A fresh sentence, same pattern — your words stay on your device.
depends on · just nowYour practice queue
due nowThe timeline depends ___ the client.
Never again. This one’s yours now.
Fill the blank.
That’s the old habit. Try the other one.
depends on · next review in 3 days
You’ve fixed this one before. Remember?
It’s 6pm and you’re re-reading a two-line email to your manager. Again.
You pause on “a” or “the” — the same pause as last week, and the week before.
The squiggly line flags “depends of”. You accept the fix. Maybe for the 40th time.
The tool fixed it. You didn’t learn it. Tomorrow you’ll type it again.
Fixing is not learning.
Cloud grammar checkers
- Fix the sentence
- Read your text on their servers
- You need them forever
MistakeMate
- Trains the writer
- Never sees your text
- Built so you need it less every week
How MistakeMate works
Write like you always do
The extension checks your writing right on your device as you type in Chrome, even offline. No account needed for checking.
Accept a fix
When you accept a correction, MistakeMate records the pattern (“depend on”, not “depend of”). Never your words.
Practice what you miss
Your patterns become short drills, scheduled with FSRS, the modern spaced-repetition method used in Anki. The fix finally sticks.
Private by architecture, not by promise.
When you accept a correction, the record MistakeMate keeps looks like this:
prepositions.verb-dependent.depend-on · seen 3 timesNot the sentence, not the paragraph: there is no field for your sentences in our database.
- Checking runs on your device with Harper, an open-source grammar engine that works inside your browser. Nothing is sent anywhere to be checked.
- It works offline. Unplug the Wi-Fi; the squiggles keep coming.
- Our automated tests plant fake secret sentences and fail if one ever appears in our database, an API response, or a sync payload.
- Practice exercises are fully synthetic. They’re never built from anyone’s writing.
MistakeMate vs. Grammarly vs. LanguageTool
Here’s where the three differ, from their own public pages.
| MistakeMate | Grammarly | LanguageTool | |
|---|---|---|---|
| Where checking happens | Your device — even offline | Their cloud servers | Their servers in Germany (self-hosting possible) |
| Your text | Never leaves your device | Processed on their servers; de-identified samples may train models unless you opt out | Processed on their servers; they say texts aren’t stored or used for training |
| Learning from mistakes | Every accepted fix becomes spaced practice (FSRS) | Explains rules as it corrects; no practice | Explains rules as it corrects; no practice |
| Price — corrections | Free, forever | Free (basic) · Pro from $12/mo (annual) | Free (basic) · Premium from about €5/mo (annual) |
| Price — learning practice | $9/mo billed annually · $15 monthly | Not offered | Not offered |
Where checking happens
MistakeMate Your device — even offline
Grammarly Their cloud servers
LanguageTool Their servers in Germany (self-hosting possible)
Your text
MistakeMate Never leaves your device
Grammarly Processed on their servers; de-identified samples may train models unless you opt out
LanguageTool Processed on their servers; they say texts aren’t stored or used for training
Learning from mistakes
MistakeMate Every accepted fix becomes spaced practice (FSRS)
Grammarly Explains rules as it corrects; no practice
LanguageTool Explains rules as it corrects; no practice
Price — corrections
MistakeMate Free, forever
Grammarly Free (basic) · Pro from $12/mo (annual)
LanguageTool Free (basic) · Premium from about €5/mo (annual)
Price — learning practice
MistakeMate $9/mo billed annually · $15 monthly
Grammarly Not offered
LanguageTool Not offered
Sourced from each product’s public pricing and privacy pages, August 2026.
Why MistakeMate exists
I kept accepting the same fixes in every message I wrote — “depends of”, “informations”, the missing third-person “-s” — and none of my tools ever made me stop. I built MistakeMate to be the tool that finally does: it notices what I repeat, and it drills it out of me.
Gustavo SteinmetzFounder, MistakeMate
Common questions
What does it cost?
Checking and corrections are free, forever. The learning experience — the practice queue built from your own mistakes — is $9 a month billed annually, or $15 month to month.
What exactly do you store about my writing?
A concept ID and a count, like prepositions.verb-dependent.depend-on · seen 3 times. Your sentences never leave your device. There is no field for them in our database.
Do I need an account?
Not for checking — that runs on your device with no account at all. An account keeps your practice queue and progress in sync across devices.
Will it catch as much as Grammarly?
It focuses on the patterns non-native writers actually repeat: articles, prepositions, tense, agreement. A cloud checker may flag more one-off typos, and the trade is that it reads everything you type on its servers. Our bet is that fixing the mistakes you repeat matters more than catching every rare one.
Which browsers and apps does it support?
Chrome first, via the extension. That covers Gmail, Slack and Docs in the browser tab, GitHub, and anywhere else you write in Chrome. Desktop apps can't be reached by a browser extension; more platforms are on the roadmap. The practice app itself runs in any browser.
How is this different from Grammarly?
Grammarly corrects you on its servers and moves on. MistakeMate turns each fix you accept into spaced practice on your device, so the mistake stops coming back. The full comparison is in the table above.
Start unlearning your mistakes.
Checking on your device. Practice built from what you actually get wrong.
Get started freeCorrections free forever · learning plan $9/mo billed annually