Grammar Checker (Offline)

Grammar Checker (Offline) is an extension that lets you check American English grammar for any input text.

To work with this addon, please open the app interface by pressing the toolbar button. By default, the interface opens in a standalone window. However, you can also open it in a separate tab or in a toolbar pop-up. To do so, right-click the toolbar button and choose the desired context from the context menu. Once the app interface is open, please write or paste a text; you can also drag a ".txt" file into the text area on the left side. Then, wait for the app to perform the grammar checks; you can see the grammar suggestions on the right side. For a reasonable-length text (a page or two), the time required to perform the check is usually around a few seconds. You can review each grammar suggestion and either accept or dismiss the item.

Note 1: This extension uses two different AI engines for grammar check. The first one is the local Harper.js engine (https://github.com/Automattic/harper), and the second one is the built-in Gemini Nano AI (https://developer.chrome.com/docs/ai/proofreader-api). To activate Gemini Nano, please mark the checkbox in the top-right corner of the interface. When you run the app for the first time, Gemini Nano needs to download training and language data. Please be patient while it is loading, as the data is quite large (~3.5GB). Once the app is fully loaded, it can work fully Offline and does NOT rely on any servers to send or receive text.

Note 2: If the built-in Gemini Nano AI is not activated in your browser, the app will notify you, and you need to manually enable it by setting the following flags to Enabled:

chrome://flags/#proofreader-api-for-gemini-nano

chrome://flags/#optimization-guide-on-device-model