Privacy · October 29, 2026

What happens to your text when you use an online grammar checker?

By PWA Team

The round trip, step by step

1. You type in a text box. The extension or app reads the text, usually a sentence or a paragraph at a time, often while you're still typing.
2. The text travels over the internet to the provider's servers, encrypted on the way.
3. A model on those servers checks it and sends back a list of suggestions.
4. Your browser draws the underlines. The trip takes a fraction of a second, so it feels as if it happened on your computer.

There is nothing sinister about this. It's how most online software works. But it does mean that a copy of your text has been on someone else's computer, and what happens to it next is decided there, not by you.

What the provider decides

Once the text reaches a server, the provider's policy answers a handful of questions: whether it is stored, for how long, who on their side can read it, whether it is used to improve their products or train models, and which other companies, such as hosting or AI providers, handle it along the way.

Reputable providers answer each of these in their privacy policy, and many offer settings, for example to keep your text out of product improvement. Check the defaults as well as the options. A setting that is on until you find it applies to everything you wrote before you found it.

Why it matters more for some text than others

For a birthday message it hardly matters. It matters for exactly the writing people most want checked: a contract draft, a performance review, a letter about a patient, a reply to a lawyer, an application you write on a work laptop.

Many employers don't allow such text in outside services at all, however good the provider's promises are. Personal details about other people often come with legal duties too, whichever tool you use.

What changes when the check runs on your device

An on-device checker runs the model on your own computer. The round trip above loses its second step: the text is read, checked and underlined in the same place it was written. There is no copy elsewhere that could be stored, read or used for training.

Private Writing Assistant works this way. It uses Chrome Built-in AI, a model Chrome downloads once and runs locally, so what you write on websites is never sent to us, to an AI service or to anyone else. Two things can leave your device, and neither contains your text: usage stats, which you can switch off, and feedback you choose to send. The privacy policy lists every detail.

The trade-off is hardware. A local model needs a fairly recent computer and free disk space; Will it run on my computer? explains what exactly.

Four questions to ask any checker

1. Where is my text checked: on my device or on a server?
2. If it goes to a server, is it stored there, and for how long?
3. Is it used to train or improve models, and is that switched on by default?
4. Do I need an account, and what does that account connect my text to?

If a tool can't answer these in plain words, treat what you type into it as shared. Our guide to private grammar checkers goes through the same questions for several popular extensions, with their own pages as sources.