Highlighting Matches in Your Doc (and Clearing Them)

Updated September 26, 2026

Short answer

After a check in the Google Docs™ add-on, tick Highlight matches in document (Plagiarism tab) or Highlight AI sentences in document (AI content tab). Matches get a pale red background and AI-likely sentences a pale yellow one. Click Clear to remove the add-on’s highlights — any highlight colour you had applied yourself comes back.

Turn highlights on

Highlight results in your document

Run a check from Extensions › Plagiarism Checker Plus › Check this document.
In the Plagiarism tab, tick Highlight matches in document. Every matched passage gets a pale red background.
In the AI content tab, tick Highlight AI sentences in document. Flagged sentences get a pale yellow background.
Wait for Updating highlights… to finish. On long documents this can take a moment.

Highlights start off, so the add-on never changes your document until you ask. Once you’ve turned a highlight on, later checks of the document highlight their results automatically; untick the box to stop.

Jump to a single match

You don’t need highlights to find a match. Click any source row, match or AI passage in the sidebar (or its Show in document button) and the add-on selects that text in the document, scrolling it into view. If you see Couldn’t find it in the document, the text has been edited since the check — run Re-check to refresh the results.

Clear the highlights

Click Clear in the sidebar. It removes only the highlights the add-on added. If a passage already had a background colour before (for example your own yellow highlighter), that colour is restored. Your text, comments and other formatting aren’t touched.

Clear before you submit or share the document, so readers don’t see the colours.
Unticking the highlight box and clicking Clear are different: unticking stops future checks from highlighting; Clear removes what’s already there.
Changing Docs’ own highlight colour over a passage the add-on marked works like any edit — the add-on won’t overwrite your change.

Why highlights may be missing

The text changed. If you see Nothing to highlight. The text may have been edited since the check, the matched wording no longer exists in the document. Re-check to highlight the current text.
Excluded text isn’t highlighted. Quotes and reference lists you chose to leave out weren’t checked, so they can’t match. See Leave out quotes and your reference list.
You checked a selection. Only the selected part was checked, so only that part can be highlighted.
Low-probability AI sentences (below 40%) aren’t listed or highlighted.

Highlights are part of the document, so collaborators with access will see them until you clear them. They’re stored as ordinary background colours plus named ranges the add-on uses to find and clear its own highlights later.

New to the add-on? Start with How to check for plagiarism in Google Docs or How to check a Google Doc for AI writing.