Google is adding an important missing feature to the Google Docs web app, the ability to cross-check documents and compare them. With Google Docs, users will be able to check two documents and see whatever differences exist between them.
The firm says it is useful for educators to compare essays and for business users to track changes in the contract. For students and writers, it can also be useful to check out changes between essay drafts.
Google will be rolling out this feature from the 11th of June, so you should see it pretty soon if not already.