Display the use of iframes in Firefox

Check iframe is a free open source browser extension for Firefox that reveals to you if websites use iframes and highlights the iframe code and the actual iframe on the website.

Websites may use iframes to display other HTML documents in a frame. It is often used by advertising scripts, social media scripts or media embeds.

While iframes are certainly useful in some contexts, they may cause privacy issues and concerns as well. Companies may read previously set cookies for example and they may gain access to data such as a device's IP address, web browser, and other information.

You can check the source code of any website to find out about iframe use. Tap on F12 to display the Developer Tools of the browser that you use and switch to the source code listing there (in Firefox that is Inspector). You can use the search to find instances of iframe. It works, but it is time consuming if you want to do so for multiple sites or even all sites that you visit.

Check iframe

Check iframe simplifies the process. The extension adds an icon to Firefox's main toolbar when you install it that uses color codes to highlight the use of iframes on webpages that you open in the web browser.

The extension supports for different color codes currently:

• Blue icon -- not checked.
• Green icon -- no iframes detected.
• Orange icon -- at least one iframe detected.
• Purple icon -- iframe detected and at least one matches a custom source added by the user of the extension.

The extension uses the JavaScript function document.getElementsByTagName() to detect iframe tags on websites.

A click on the icon displays options to run another scan for iframes on the page, scroll to the next detected iframe element and highlight it by drawing a red border around it, display the source of all tags found, or open the built-in configuration.

The configuration offers two options: you can enable log output to the console in Firefox and add custom sources to the extension so that you are notified whenever the source, e.g. an iframe by Facebook, is found on a page.

Closing Words

Check iframe is a useful privacy and maybe also development extension. It highlights when pages on websites use iframes, displays the code of the iframes, and highlights them on the page. It provides you with the means to spot small iframes used for tracking, and any iframe a site uses.

I would like to see an option to highlight all iframes on a page at the same time. The extension highlights only one at a time right now.

Now You: Do you analyse the code of sites you visit?