Sites opened in mobile devices should meet certain criteria in order to load successfully. Google's testing tool is available to keep check and balance but it lacks consumer's convenience along with many other functional issues.

Bing announced the launch of their incredible mobile friendliness test tool on Thursday. The actual release  was delayed and should be last May.  The tool assesses a certain page to determine if it is mobile-friendly based on some criteria.  These include viewport and zoom control configuration, width of page content, page text readability, links spacing and other elements and usage of incompatible plug-ins, as reported by the Search Engine Island. 

"The Zoom Control check verifies if the configuration of the viewport hampers the user's ability to pinch and zoom the page," Microsoft senior program manager of webmaster tools Charu Puhazholi and mobile ranking program manager Shyam Jayasankar wrote in a blog post on the Mobile Friendliness Test Tool. "In general, not using the scale-related viewport settings should result in your page being zoomable on most mobile browsers, but improper use of these settings (user-scalable, maximum-scale, minimum-scale) could result in hampering access to some content on the page. Some mobile-friendly pages prevent user zoom by design and we do take that into account before flagging it as an error.", Venture Beat reported.

If any of these criteria is not met by Bing, due to blocked resources or any other reason, the testing tool will notify you instantly for the user to correct the problem.

According to Search Engine Journal, Bing's tool is somewhat similar to Google' mobile-friendly tool in a way it return an overall decision as to whether or not the site is mobile-friendly.  This depends on how much of the above criteria is met but if a page fails, the testing tool will notify the reasons. 

However, compared to Google's testing tool, Bing's tool is much faster and more user-friendly in its presentation.  If speed and presentation is more important to you, then Bing's new tool is for you.