Starting with April 21st, 2015, Google will change the algorithm for searches originating from mobile devices to favor websites that are optimized for smartphones. This change will affect searches in all languages worldwide and will have a “significant impact in our search results”, according to Google.
Web developers can determine with Mobile-Friendly Test if a web page is considered mobile-friendly by Googlebot. The respective online tool provides reasons on why a page failed the test and some advice on how it can be fixed. The tool works for manually checking individual web pages. For validating entire websites, developers are recommended to use the Mobile Usability Report from Webmaster Tools.
To consider a web page as mobile-friendly Googlebot checks for the following conditions to be met:
- the page is not using desktop plug-ins such as Flash
- the text is large enough to be read without zooming in
- content is visible without horizontal scrolling or zooming
- there is enough space between links so a user can tap one without risking to activate another one
The Mobile-Friendly Guide provides advice on how to make a website friendly to mobile users, with explanations on Responsive Website Design, the Vary HTTP header, alternate and canonical tags, dealing with tablets or feature phones, and others.