A distributed-client change-detection tool detects changes in Internet
web-page documents on the world-wide-web. To register a web page for
change detection with a change-detection server, a user specifies the web
page's URL. A client-side change-detection application is downloaded to
the user's client from the change-detection server. The server assigns a
date and time for the client to perform change detection. At the assigned
time and date, the client fetches a new copy of the web page and compares
it to an archived copy to detect changes. When the client detects a
change, it sends a notification with the URL to the server. The server
verifies that the change has not already been reported by another user's
client and then notifies all users of the registered web page. As more
users are registered for a web page, change detection is performed more
frequently. The most popular pages with tens of thousands of registered
users are checked every few minutes. Each user is notified within minutes
of any changes in the registered web page, even though any one user only
performs change-detection once a month. Checksums rather than entire web
pages can be stored and compared to reduce storage requirements at the
server. The change-detection server performs its own change-detection for
less popular web pages. More popular web pages are checked more frequently
using the additional client resources of the users.