How to install and use LineCheck

Install from the Chrome Web Store

1. Open the official LineCheck listing in desktop Chrome.
2. Choose Add to Chrome and review the extension permissions.
3. Open or refresh an ordinary article webpage, click the LineCheck icon, and start Focus.

Alternative: install the open-source version

LineCheck is free and open source. Use desktop Chrome 120 or later.

1. Open the LineCheck source repository, choose Code → Download ZIP, and extract the archive.
2. Enter chrome://extensions in Chrome’s address bar and turn on Developer mode.
3. Choose Load unpacked and select the linecheck-extension folder containing manifest.json.
4. Open or refresh an ordinary article webpage, click the LineCheck extension icon, and start Focus.

Keep the extracted source folder. After updating its contents, reload the extension and refresh the article. Choose the interface language in the popup.

Keyboard controls

Repeating a mark clears it; choosing the other mark replaces it. Marking does not move to the next line.

To choose a global Focus shortcut, open chrome://extensions/shortcuts. The assigned shortcut can differ by extension version or your Chrome settings. Choose another combination if it conflicts with your browser or another extension.

A simple reading and review workflow

1. Start Focus and read the clear current line. Use the arrow keys to move at your own pace.
2. Press Enter after reviewing a passage. Use F for text you want to revisit.
3. Use left and right arrows to adjust the magnified line without resizing the original article.
4. Press Esc when finished. Marks remain visible; returning to the same full URL attempts to restore saved state.

Marks and reading records are local to this browser profile. They are not synced across devices. The extension does not automatically check grammar or spelling.

Troubleshooting

Focus does not start

Refresh the article after installation. Chrome internal pages, the Chrome Web Store, and built-in PDF viewers do not allow this reading guide. Try an ordinary HTML article.

Some text is skipped

Image text, canvas content, embedded frames, and Shadow DOM are unsupported. Complex or dynamically changing layouts may not work reliably.

My highlights did not return

Confirm the full URL is the same, including query and fragment. Restoration needs a unique matching text anchor; edited articles or repeated text can prevent it.

Can I use a local HTML file?

Enable Allow access to file URLs in the extension’s Chrome details. Local PDFs remain unsupported.

How do I remove records?

The popup’s clear action removes marks and saved reading position for the current page. Some page metadata remains. Uninstalling removes extension-local storage; separately exported files remain. Read the privacy policy for the full retention details.