How to Install and Use the Google Docs Add-on

Updated September 26, 2026

Short answer

In Google Docs™, go to Extensions › Add-ons › Get add-ons, search for Plagiarism Checker Plus and click Install. Then open any document and choose Extensions › Plagiarism Checker Plus › Check this document to open the sidebar and sign in. To remove it later, go to Extensions › Add-ons › Manage add-ons.

Plagiarism Checker Plus for Google DocsComing soon

Check a document for plagiarism and AI writing, highlight matches, and add citations. The store listing isn’t live yet — see the product page for updates.

Learn more

Install the add-on

Open any document in Google Docs.
Choose Extensions › Add-ons › Get add-ons. The Google Workspace Marketplace opens in a window.
Search for Plagiarism Checker Plus and open the listing.
Click Install and choose your Google account.
Review the permissions Google shows you and click Allow to finish.

What the add-on can access

The add-on asks for three things: to view and edit the document it’s opened in (to read the text and to add highlights or citations when you ask), to show its sidebar, and to connect to Plagiarism Checker Plus. It can’t see your other documents, your Google Drive, your Gmail or your Google profile. Your document text is sent to us only when you click Check. More in What happens to the text I check?

Sign in and run your first check

In a document, choose Extensions › Plagiarism Checker Plus › Check this document.
Click Sign in. A window opens on the Plagiarism Checker Plus website.
Sign in, or create a free account. Then click Connect Google Docs to link this add-on to your account.
Go back to your document. The sidebar finishes signing in by itself and shows your words left.
Choose what to check (whole document or selection), tick Plagiarism and/or AI-generated text, and click Check document.

If nothing happens when you click Sign in, your browser may have blocked the pop-up. Allow pop-ups for Google Docs in your browser and try again. The sign-in link is valid for a few minutes; if it times out, just click Sign in again.

Everyday use

Open the sidebar any time from Extensions › Plagiarism Checker Plus › Check this document. It remembers the last check for each document.
Extensions › Plagiarism Checker Plus › Help shows quick instructions and how to contact support.
The Account section of the sidebar has Sign out.
Related guides: checking for AI, checking for plagiarism, highlights, excluding quotes and references and citations.

Remove the add-on

In Google Docs, choose Extensions › Add-ons › Manage add-ons.
Find Plagiarism Checker Plus, open its options menu and choose Uninstall.
To also withdraw the access you granted, visit myaccount.google.com/permissions, select Plagiarism Checker Plus and remove its access.

Signing out in the sidebar removes the sign-in token from your Google account. Uninstalling doesn’t delete your Plagiarism Checker Plus account or your check history; to delete those, email contact@plagiarismcheckerplus.com.