Whenever you install an application or extension in the Chrome browser, you are asked to confirm the permissions that the program requests.
That's your only indicator as to what the extension or app may access in terms of data and modify in the browser.
Up until now it was not really possible to check an extensions or apps data usage after it has been installed in the browser.
The Chrome Apps & Extensions Developer Tool changes that for the better.
You can use it to look up the recent activity history of any application or browser add-on as well as real-time information.
To use it simply launch the application once it has been installed in the browser. The list of installed apps is displayed by default which you can switch to extensions with a click on the link in the window.
If you have installed many, you can also use the search to find any app or extension this way.
Besides options to display permissions of any app or extension, it is also possible to check its behavior.
When you click on the link, the programs recent history is displayed to you.
The information displayed here are extensive. While they are intended mainly for debugging purposes, they can also provide end users with useful information about extension and app activities in the browser.
The app displays privacy-related activities at the top and all recent history events below that.
Here you can find out if an app or extension modified web pages and if it did which functions it used for that, if it communicated with a web server, or checked for program updates.
You can switch to realtime here to display events as they happen. The information are similar on the page with the exception that they are sorted by time and not function.
You will also notice that each activity is displayed on its own instead of being grouped together as is the case on the history page that the app provides you with.
If you are not a developer, you may still use the app to verify an app's or extension's activity in the browser. While that may mean additional research -- unless you know what activities such as "invoked XMLHttpRequest.open" or "i18n.getMessage" do -- as it may not be clear at all times what a certain activity does.
Sometimes though you get additional useful information when you click on the arrow icon next to a command. Here you may for instance see the url that the extension or app queried.
The Chrome Apps & Extensions Developer Tool is a useful application for Chrome that developers and end users alike can make use of.
The main feature that makes it for end users is to verify the requests an applications make, for instance to find out to which servers it connects on the Internet when it runs.