How ChatFix works
1. Your messages
You upload a WhatsApp chat (or a voice note), or type a message into Check before I send. Only your messages are checked. Other people's messages are used only as context so the AI understands what you meant. Chat text is deleted after checking; only the corrected messages are kept.
2. Mistakes and habits
One AI pass finds the mistakes and a second pass double-checks them. Each one gets a correction, a more natural version and a short explanation. Mistakes you repeat are grouped into habits, so you learn one rule and fix many messages. If something is not a mistake, hide it from the ⋯ menu.
3. Practice
Each card shows what you wrote and, when it helps, a hint about what you meant (never the answer). Write it correctly or just reveal the answer, then rate it. Cards you know come back later, hard ones sooner (a Leitner box system).
4. Your level (A1–C2)
ChatFix estimates your CEFR level from your own writing only: your chat messages and the messages you check. It never uses other people's messages, voice notes, or text that looks AI-written or machine-translated. Those are spotted with simple signals (assistant phrases, long dashes, polished long paragraphs) and, when unclear, a quick AI check. You can also mark any message Not mine from its ⋯ menu.
- Grammar: which structures you use, with levels from the English Grammar Profile (for example present perfect is B1, third conditional is C1).
- Vocabulary range: how many less common words you use (word frequency bands).
- Fluency: how long and connected your sentences are.
- Accuracy: mistakes per 100 words.
It looks at your newest 300 messages from the last 90 days and needs at least 20 messages before it shows a level. The level only changes from new writing, and only when the evidence is clearly past the boundary, so it does not jump around. It is an estimate, not an official certificate.
The bar shows how far you are towards the next level. If you don't practise for more than 3 days it fades by about 1% a day, but never below the start of your level. Practise again and it comes back.
5. Streaks and freezes
One practice session or one check a day keeps your streak. Days follow your own timezone. Every 7 days in a row you earn a streak freeze (you can hold 2). A freeze covers a missed day automatically. Streaks are saved on our server, so they work across devices.
6. Milestones
First session; streaks of 3, 7, 30, 100 and 365 days; 10, 100 and 500 mistakes fixed; a habit beaten (a repeated mistake gone for 2 weeks while you kept writing); a new level; a perfect session; your first streak freeze.
7. Reminders
Turn on a daily email reminder in Settings and pick a time. You get at most one a day, only if you haven't practised yet, and it tells you when your streak is at risk.
Word frequencies: wordfreq by Robyn Speer (CC BY-SA 4.0). Grammar levels inspired by the English Grammar Profile.