Page Monitor is a useful Chrome add-on that stays in the background and monitors web pages for changes. If it detects a change in any of the monitored pages, you get a desktop notification or you may choose to receive sound alerts.
You may click the alert to compare the difference between the old and new versions of the page visually.
To get started, open the web page that you would like to monitor, click on the Page Monitor icon and select “Monitor This Page”. Alternatively, you may switch to the Advanced view and visually select a particular area (div) of the page for tracking.
Page Monitor also supports regular expressions (regex) for monitoring a specific element on a page. For instance, you may only be interested in monitoring the price of a product on Amazon and would not like to be informed when a new customer review is added to the Amazon Product page. That’s where regex would help.