Private Grammarly alternatives: what each one sends to a server
The most private Grammarly alternative for grammar checking is Harper: it runs on your device and sends nothing anywhere. LanguageTool can also run as a server on your own computer, without its AI rules. For AI rewriting and replies rather than grammar underlines, ShroomPen or Scramble connected to a local model (Ollama or LM Studio) keep your text on your machine. Grammarly, LanguageTool’s cloud service and DeepL Write process your text on their own servers, and DeepL’s free tier may use it to train its models.
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What each tool sends, and where
| Tool | What it does | Where your text is processed | Used to train AI? |
|---|---|---|---|
| Grammarly | Grammar checking and AI writing | Grammarly’s (Superhuman’s) servers | Controlled by a training setting in your account |
| LanguageTool, cloud | Grammar and style checking | LanguageTool’s servers | No, according to its privacy policy |
| LanguageTool, own server | Grammar checking without the AI-based rules | Your computer | No, nothing is sent |
| DeepL Write, free | AI rewording | DeepL’s servers | Yes, kept for a limited period for training |
| DeepL Write Pro | AI rewording | DeepL’s servers, kept only temporarily | No |
| Harper | Grammar checking, English only | Your device | No, nothing is sent |
| Wandpen, free tier | AI writing with Chrome’s Gemini Nano | Your device, for the Gemini Nano features | No, for on-device use |
| Scramble + local model | AI rewrites of selected text | Your computer (Ollama or LM Studio) | No, nothing leaves your machine |
| ShroomPen + local model | AI replies, rewrites, grammar fixes and translation in any text field | Your computer (Ollama, LM Studio or another localhost server) | No, nothing leaves your machine |
| ShroomPen + your API key | Same | The provider you chose (OpenRouter, OpenAI, Anthropic or Gemini), directly from your browser | Depends on that provider’s terms. ShroomPen itself receives nothing |
Based on each company’s own privacy policy, docs or README, read on 26 September 2026. ShroomPen is our product. We list it with a local model first because that is the private setup; with a cloud key your text goes to that provider.
Harper: the private grammar checker
Harper checks spelling, capitalization and grammar entirely on your device: its site says every check happens locally, with no cloud round-trips, no telemetry and no LLM. It is free, open source (Apache-2.0) and has a Chrome extension. It supports English only, in several regional variants, and it fixes mistakes rather than rewriting your text.
LanguageTool: cloud by default, self-hosting possible
The LanguageTool browser add-on sends your text to LanguageTool’s servers. Its privacy policy says this includes content of the websites you use it on, and that it does not use any user’s input to train its models. If you want nothing to leave your computer, you can run a LanguageTool server locally and select “Local server” in the add-on’s experimental settings. The local server has no AI-based rules and no synonyms; those exist only in the cloud.
DeepL Write: private only on Pro
DeepL Write rewords text on DeepL’s servers. Its privacy policy separates the free and paid versions: free texts may be kept for a limited period to train and improve its models, while Pro texts are kept only as long as needed to produce the result and are not used for training.
Wandpen: on-device AI with Gemini Nano
Wandpen’s free tier includes unlimited writing with Chrome’s built-in Gemini Nano, which runs on your device and works offline. It also offers cloud models on its $10 a month Pro plan and a $19 lifetime plan for your own API keys. Its homepage doesn’t describe the data path for the cloud options in detail, so check its privacy policy if you plan to use them.
Scramble: open source, any provider
Scramble is an MIT-licensed Chrome extension that rewrites selected text from the right-click menu. It works with OpenAI, Anthropic, Groq and OpenRouter, and with local models through Ollama or LM Studio. With a local model, your text stays on your computer. Its maintainer says it is no longer actively developed.
ShroomPen: AI writing in any field, with your model
ShroomPen is a free Chrome extension that drafts, rewrites, fixes grammar and translates in the text field you are using. It has no server of its own: requests go from your browser straight to the model you set up. With Ollama or LM Studio on your computer, nothing leaves the machine. With a cloud key (OpenRouter, OpenAI, Anthropic, Gemini), the text goes only to that provider.
- It reads the page, the field, selected text or other tabs only when you switch that source on for a request.
- It skips password, one-time code, card and other sensitive fields.
- It sends no telemetry, has no ShroomPen account and keeps keys in Chrome’s local extension storage.
- It is closed source and Chrome-only, and it does not underline mistakes as you type.
Full details: how ShroomPen handles your data. Local setup: Ollama or LM Studio. Get ShroomPen on the Chrome Web Store.
Which one to pick
- Confidential text, and you only need grammar and spelling in English: Harper.
- Grammar checking in other languages, and you can run a Java server: LanguageTool on your own machine.
- AI rewriting and replies with nothing leaving your computer: ShroomPen or Scramble with Ollama or LM Studio.
- AI help without installing a model or getting a key: Wandpen’s Gemini Nano tier.
- High-quality rewording in a web app, and you can pay: DeepL Write Pro.
Related
Questions
What is the most private alternative to Grammarly?
Harper. It checks English grammar and spelling entirely on your device, with no cloud requests and no telemetry, and it is free and open source. It does not rewrite or draft text with AI.
Is there a Grammarly alternative that works offline?
Harper works offline. LanguageTool works offline if you run its server on your computer and point the browser add-on at it. For AI rewriting offline, use ShroomPen or Scramble with a local model through Ollama or LM Studio.
Does ShroomPen check grammar as I type, like Grammarly?
No. ShroomPen does not underline mistakes. It has a Fix Grammar button next to the text field you are in: click it and your model rewrites the field’s text with the mistakes fixed. It is an AI writing assistant, not a live grammar checker.
Does Grammarly use my writing to train AI?
Grammarly’s privacy policy, now published by its parent company Superhuman, says you can decide whether your content is used to train its AI models with the training controls in your account settings. Your text is still processed on its servers either way.
Is DeepL Write private?
Its paid Pro plan is the private one: DeepL says Pro texts are kept only temporarily and are not used to improve its services. On the free version, DeepL says it may keep texts for a limited period to train and improve its models.