can you check to see if a site has mobile layout without using a small screen?

will sites check this or must it be loaded on a small screen?

 

Yes you can check this quite easily by simply making the browser window smaller. If the website is responsive, it will change size to fit the size of the browser. The website could have a mobile only version though, so the best way to check if you want to be sure is using Googles mobile friendly test tool:
https://www.google.com/webmasters/tools/mobile-friendly/

 

Use this

https://www.responsinator.com/

 

Try these:
Google’s Mobile-Friendly Test
W3C mobileOK Checker
BrowserStack
mobiReady (beta)

 

1.Right click on the website
2.Inspect element
3.click on the thing next to the magnifier

 

Are you using Firefox? Wait, it's in a different spot in Firefox.

 

This is the best we've used so far: http://quirktools.com/screenfly/