HTML Diff Check Tool is a free Chrome add-on developed by scott. This tool allows users to check differences between HTML tabs or between a production and development environment. It is particularly useful for web developers who want to compare the HTML sources of different web pages.

With HTML Diff Check Tool, users can easily compare the HTML differences between a testing and production environment before or after deployment. It is also handy when a co-worker asks for a check on a testing environment they have updated.

Using the tool is straightforward. Users can register the combination of a testing and production environment domain in the settings. They can then turn on the "balance scale" icon or select from the context menu on the web page they want to check. By clicking the "open" button, the testing or production environment domain will be opened. Users can also click the "diff" button to check the difference between the HTML sources.

Privacy-wise, the tool analyzes traffic data via Google Analytics. However, the registered domains, URLs, or HTML sources are not sent to third parties.

Overall, HTML Diff Check Tool is a valuable add-on for web developers who need to compare HTML differences between different web pages or environments. Its user-friendly interface and convenient features make it a useful tool in the web development process.