Grammar Checker That Never Uploads Your Text — Fully Private, No External Servers
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Every major online grammar tool sends your text to their servers. Grammarly sends every keystroke to Grammarly Inc. ChatGPT sends it to OpenAI. Google's grammar suggestions in Docs send it to Google. That's how all of them work — and it's fine for a grocery list or a tweet.
It's not fine for a legal brief, a medical record, a confidential business proposal, or anything else you wouldn't want on someone else's servers.
Our grammar checker is different: it processes your text in your browser using on-device AI. Nothing is transmitted. This guide explains exactly how that works, who it matters for, and how to verify it yourself.
What Actually Happens to Your Text With Common Grammar Tools
Grammarly: When you type with the Grammarly extension, your text is sent to Grammarly's servers for processing on every keystroke. From their privacy policy: "We collect your writing to provide the Services." Grammarly says they don't sell your data to third parties, but your text exists on their infrastructure, subject to breaches, legal requests, and their own internal analysis.
ChatGPT: Text you submit to ChatGPT's web interface may be used to train future models by default. You can opt out in settings, but the default is opt-in data collection. OpenAI's privacy policy describes how they collect, store, and use prompts.
Google Docs grammar suggestions: Google processes your document content to provide grammar suggestions. Your document content is stored on Google's servers as part of the service — this is explicit in their terms.
None of this is secret. These are the legitimate business models of cloud software services. But for text that contains sensitive information, sending it through these services means it leaves your control.
How Local Browser Processing Works
Our grammar checker uses AI capabilities built into modern browsers — specifically, the on-device language model that browsers like Chrome make available to web applications. When you run a grammar check:
- Your text is passed to the browser's on-device AI engine
- The AI processes the text on your device's processor
- Corrections are returned to the browser tab
- Nothing is transmitted over the network
You can verify this. With the grammar checker page open and your text pasted in, open Chrome DevTools (F12) and click the Network tab. Click Fix Grammar. Watch the network requests — for the actual grammar processing, there are no outbound requests. The computation happens locally.
This is meaningfully different from any server-side grammar service. Your text is never in transit, never on a third-party server, and never subject to that server's security or business decisions.
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Most people can use any grammar tool with minimal risk. But for certain content and certain professions, local processing is important:
Legal professionals: Attorney-client privileged communications and work product must be protected. Uploading client documents to cloud grammar services creates potential privilege concerns that many law firms prohibit by policy. See our detailed guide on grammar correction for legal documents.
Healthcare workers: HIPAA regulates protected health information. Running patient records or clinical notes through cloud AI tools could constitute a violation depending on the use case and the service's compliance status.
Financial and accounting professionals: Non-public financial information, M&A documents, and earnings data are subject to securities regulations. Uploading these to cloud services before public disclosure creates exposure.
Academic researchers: Unpublished research and pre-print papers can be unintentionally shared through cloud services. For work that needs to remain confidential before publication, local processing avoids this risk.
Corporate employees: Trade secrets, product roadmaps, personnel records, and confidential business plans. Many companies have explicit IT policies prohibiting cloud AI tools for internal content.
Practical Difference: Local Processing vs Cloud Processing
For day-to-day grammar checking of ordinary text, there is no practical quality difference between local and cloud processing. Both catch grammar and spelling errors accurately.
The differences that matter:
| Factor | Cloud Grammar Tools | Local Browser Tool |
|---|---|---|
| Text location | On third-party servers | On your device only |
| Data retention | Varies by service | Gone when tab closes |
| Breach risk | Subject to service's security | Not applicable |
| Legal exposure | Potential issues for privileged content | No exposure |
| Offline use | Requires internet | Works after page loads |
| Speed | Network-dependent | Fast (no network round trip) |
For sensitive content, local processing is strictly better. For ordinary content, it's a wash — with the small advantage of being faster because there is no network round trip.
How to Verify Any Grammar Tool's Privacy Before Using It
Before pasting sensitive text into any grammar checker, do a quick verification:
Check the network traffic: Open the browser DevTools (F12) > Network tab. Paste text and run the check. If you see outbound POST requests while the grammar check runs, your text is being sent somewhere. Our tool shows no outbound requests during processing.
Read the privacy policy: Look specifically for what they collect, how long they retain it, and whether it's used for training. Grammarly's privacy policy explicitly mentions collecting "writing content." ChatGPT's mentions using inputs for model improvement by default.
Check their compliance page: Many tools have a compliance or security page. Look for SOC 2, HIPAA Business Associate Agreement availability, and data residency options. For enterprise use, these matter.
Look for any "local processing" or "on-device" claims: Legitimate local processing tools will explicitly state this and it should be verifiable by inspecting network traffic.
Privacy in grammar tools isn't binary — it's a spectrum. For most writing, any tool is fine. For sensitive content, the verification steps above take two minutes and are worth doing.
Check Grammar Privately — No Upload, No Server
Runs in your browser. Text never leaves your device. Free, no account.
Open Free Grammar FixerFrequently Asked Questions
Does Grammarly store my text?
Grammarly processes your text on their servers, which means they receive and temporarily or persistently store it according to their privacy policy. Grammarly says they don't sell your data to advertisers, but your content does pass through their systems. For sensitive content, this is a meaningful concern.
What grammar checker is most private?
Browser-based tools that use local processing are the most private. Our grammar checker uses on-device AI with no data transmission. Microsoft Word's built-in grammar check also processes locally (for the desktop app, not the online version). Any tool that advertises "no upload" or "local processing" is making a claim worth verifying in network traffic.
Can I check grammar without sending text to a server?
Yes. Our browser tool processes text locally using on-device AI. Open the tool, paste your text, run the check — nothing is transmitted externally. You can verify this by checking network traffic in Chrome DevTools while running a grammar check.
Is there an offline grammar checker?
Microsoft Word's desktop grammar check works fully offline. Our browser tool requires an internet connection for the initial page load but processes subsequent grammar checks locally. Once the page is fully loaded, you can disable network access and grammar checking continues to work.