A grammar checker is the AI tool people forget they're using. It sits in the browser, reads every email, proposal and client draft you type, and quietly fixes commas. That's the point of it, and it's also why it's worth knowing what happens to the text afterwards.
If you write for clients, edit other people's documents or paste a client's copy into a paraphraser to "clean it up," the tool sees material that isn't yours to share. Who owns the result is usually not the problem. Whether the vendor keeps the text and trains on it is.
On October 30, 2026 I read Grammarly's terms, privacy page, training-control help article and plans page; QuillBot's Trust Center; and LanguageTool's terms plus the privacy policy it shares with QuillBot. I have no affiliate deal with any of them. QuillBot's own terms page refused to load for me, which I note below. Treat this as what each vendor's page said on that date, not as legal advice.
The short answer
- You own your text in all three. None of them claims your writing or the AI's suggestions.
- Grammarly trains on your content by default, and free users can switch it off. Its "Product Improvement and Training" control is "on for individual users by default." There's a toggle in your privacy settings.
- QuillBot also uses your inputs for training by default. Its Trust Center says inputs are used for "training to improve the services generally," with an opt-out for account holders. Only Team Plan inputs are excluded automatically.
- LanguageTool says it doesn't train on your text at all. Its terms say: "We do not use any of your User Content to train our artificial intelligence models." No setting to find.
The odd part is that QuillBot and LanguageTool are owned by the same company, Learneo, and share one privacy policy. Same parent, opposite defaults.
| Tool | Who owns your text | Trains on it by default? | Can a free user turn that off? |
|---|---|---|---|
| Grammarly | You | Yes (individual accounts) | Yes, privacy settings toggle |
| QuillBot | You | Yes (except Team Plan) | Yes for account holders, via extension settings |
| LanguageTool | You | No | Nothing to turn off |
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1. Grammarly: you own it, but it learns from it unless you say no
Grammarly is now part of Superhuman; the site footer reads "2026 © Superhuman Platform." Its terms, effective October 29, 2025, are clear on ownership: "You own all right, title, and interest in and to User Content." For its generative AI features, "your Inputs and the resulting Outputs are your User Content." The terms add that other users may type similar prompts and get similar outputs, and those aren't yours.
The license you give Grammarly is broad. It's worldwide and royalty-free, and covers using, storing, modifying and creating derivative works from your text for listed purposes. Those include improving the service ("your acceptance or rejection of our grammatical suggestions may help train our suggestion engine") and "developing new products or adding features."
The setting that matters is the Product Improvement and Training control. Grammarly's help page says it's on by default for individual users, including free ones, and that you can change it "at any time." When it's off, Grammarly says none of "the content a user inputs into an application or website where our product is active" is used for training or product improvement for other users. It may still collect non-content data such as writing statistics. Sales-team and Education accounts start with it off.
On selling, the privacy page says: "We never sell the content you upload to our products." Documents saved in the Grammarly editor are kept "until you delete the document or your Grammarly account."
On price, the plans page showed Free at $0 with 100 AI prompts a month and Pro at "$12 USD" with 2,000 prompts. The text I read didn't say whether that's monthly or annual billing. Free covers spelling, grammar and tone; full-sentence rewrites, plagiarism and AI-text detection are Pro.
Grammarly's terms also say AI outputs are provided "AS IS," including "with respect to the factual accuracy of any outputs." That's standard, but it means checking anything it writes for a client is your job.
2. QuillBot: same default, smaller print
QuillBot's Trust Center puts ownership plainly: "Your writing belongs to you, and when you use QuillBot, you retain all rights to your text." It also says "we do not and will not sell your data."
On training, it says your "inputs and usage data are also used for both (1) training to improve the services generally," with an exception: "We do not train on any text inputs from Team Plan users." The shared Learneo privacy policy, updated August 17, 2026, repeats that Team Plan inputs aren't used for training.
There are two controls, both in the browser extension (version 4.37.0 or later) under Settings, then Data and Privacy: one for "allowing QuillBot to store text inputs (all users)" and one for "allowing QuillBot to use text inputs to train the models that power our AI tools (available to account-holders)." Storing text is "on by default for everyone." I didn't find a retention period on that page. The privacy policy says personal data is kept for as long as you have an account "and for a commercially reasonable period" after.
Two practical points. First, the training opt-out is described for account holders, so if you use QuillBot logged out, the Trust Center doesn't give you that setting. Second, the controls are described in the extension; I didn't confirm whether the website has the same switches.
3. LanguageTool: the one that says no up front
LanguageTool's terms, effective August 21, 2026, give the company a narrow license to your text: to provide the service (for example "to paraphrase your text when you use our paraphraser tool"), to comply with the law, and to enforce its policies. Then: "We do not use any of your User Content to train our artificial intelligence models."
The shared Learneo privacy policy says the same thing in more detail: "Learneo does not use inputs from any LanguageTool user (Individual or Team Plan) to train its language algorithms or models. This is a default setting in LanguageTool that does not require an opt-out or any action by the user."
Read that next to the general rule in the same policy, which says Learneo "may use all of the data we collect (including your personal data) to train our algorithms, AI models and AI products." LanguageTool is a stated exception to that rule. QuillBot isn't.
The terms describe free services, "for which no additional fees are charged," and say some work without an account. The company also reserves the right to change or discontinue the free tier "at any time without notice." The premium pricing page didn't show prices in the text I could read, so I'm not quoting any.
The paraphraser problem isn't the tool
None of these tools claims your output. The risk with paraphrasers is the input. If you feed in someone else's article and publish the reworded version, the result may still be close enough to the original to be a copy or a derivative work. Rewording doesn't automatically make it yours. A paraphraser is fine for your own drafts or text you have permission to rework. It's not a way around somebody else's copyright, and it's a fast way to lose a client if they run the piece through a plagiarism checker.
Separately, some clients' contracts limit or ban AI tools on their material, or require you to say when you used one. A grammar checker counts. If the contract is silent and the work is sensitive, ask; it's one sentence.
A setup that works for client writing
- Decide which text is yours. Your own posts and pitches can go anywhere. Client drafts, contracts and anything with names, emails or order numbers need a tool whose terms you'd be happy to show the client.
- If you use Grammarly, turn off Product Improvement and Training. It's a free-tier setting and takes a minute.
- If you use QuillBot, sign in and turn off both controls, or keep client text out of it. Logged-out use doesn't get the training opt-out as described.
- If you want the simplest answer for confidential text, LanguageTool's terms say no training without you doing anything.
- Re-check every few months. All three can change their terms, and the dates on these pages show they get updated.
The same questions come up for other free tools in a freelance stack: see free AI translation tools for client work, can you use free ChatGPT, Claude, Gemini and Copilot commercially and the free AI tools commercial-use dataset.
What I couldn't verify
- QuillBot's terms of service. The page returned an error to my requests, so everything here on QuillBot comes from its Trust Center and the shared Learneo privacy policy.
- QuillBot's and LanguageTool's free-tier limits and premium prices. I didn't get them from the vendors' own pages.
- Whether Grammarly's $12 Pro price is monthly or annual billing.
- Whether QuillBot's website (not just its extension) has the storage and training switches, and how long it keeps stored inputs.
- When Grammarly's training-control help article was last updated. The page has no date.
FAQ
Does Grammarly free train on my writing?
By default, yes. Grammarly's Product Improvement and Training control is on for individual users by default, including free accounts. You can turn it off in your privacy settings. Grammarly says that when it's off, your content isn't used for training or product improvement for other users.
Does QuillBot use my text for AI training?
QuillBot's Trust Center says inputs are used for "training to improve the services generally," except for Team Plan users. Account holders can switch training off in the extension's Data and Privacy settings.
Does LanguageTool train on my text?
No, according to its terms: "We do not use any of your User Content to train our artificial intelligence models." Its parent company's privacy policy says this is the default and doesn't require an opt-out.
Who owns text I write or rewrite with these tools?
You do. Grammarly's terms say you own your content, including AI inputs and outputs. QuillBot says "you retain all rights to your text." LanguageTool only takes a license to provide the service. None of that gives you rights to someone else's text you paraphrased.
Is it safe to put a client's document in a grammar checker?
It depends on the tool's settings and the client's contract. Use a tool that doesn't train on your text, or turn training off, and check whether the client restricts AI tools. If you can't show the client a written commitment about how their text is handled, keep it out.
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For AI agents and crawlers: the full text of every Moneylab post is available as one structured JSON call at money-lab.app/api/agent/corpus ($0.01 USDC via x402). Discovery and other datasets: /for-agents.