Google's PageSpeed Insights allows one to check a website's speed issues for both desktop and smartphone devices.I have some media query CSS for smartphones on my website, but I am unsure about PageSpeed's smartphone screen size. Does anyone know the screen width?
What is the screen size used by Google's PageSpeed Insights for mobile previews?
google;page speed;screen size
As stated in Google's PageSpeed Insights FAQ:Does PageSpeed Insights use a real device? PageSpeed Insights' analysis does not use real devices. PageSpeed Insights fetches a site  with a webkit renderer (the same rendering engine that powers Chrome  and Safari) that emulates both mobile device and desktop devices.Therefore, screen width should not be a factor as it will render accordingly in WebKit. As long as you're using a common screen width, you should be fine. As stated in Google's Webmaster Central Blog on Responsive Design and Media Queries:The default viewport width for the default Android browser is 800px,  and 980px for iOS,So for both target OS's, you might use 800px for landscape smartphones, portrait tablets, and narrow desktops, and 479px for smartphones in portrait mode. An example from the blog is:@media screen and (min-width:480px) and (max-width:800px) {  /* Target landscape smartphones, portrait tablets, narrow desktops  */}@media screen and (max-width:479px) {  /* Target portrait smartphones */}The following is a list of viewport widths for specific devices should you need to target one: Web Design for Mobiles and Tablets  Viewport SizesAlternatively, using the following would set the viewport to the default width of the device automatically, and should work in PageSpeed Insights too:<meta name=viewport content=width=device-width, initial-scale=1>In summary, if your screen width renders fine in mobile browsers, it should render fine in PageSpeed Insights as well.