Our website uses an open source product to detect user agent and based on that, it servers mobile theme or desktop theme to users. I know the exact difference between mobile-friendly test and pagespeed insights as described here https://developers.google.com/webmasters/mobile-sites/references/faq#whats-the-difference-between-the-pagespeed-insights-ux-score-and-the-mobile-friendly-test-results

So if a MFT uses a normal Google bot to request the page, then of course desktop theme will be served. But where more appropriately PageSpeed Insights uses mobile user agent to request the page. So it will be served with mobile theme.

Page speed result gives 100% pass on mobile usability and in mobile devices, it loads mobile theme correctly. But on other-hand result in following link says 0% pass on mobile usability.

So now we are getting many pages marked as not mobile friendly even-though we have a mobile friendly theme.

In last few weeks when i click Mobile Usability Check link from my web master account, it loaded PageSpeed. From today its loading MFT.

I believe fetching page as normal Google bot and indexing for mobile website will have issues. I am sure there may be 1000's of websites with 2 different themes for mobile and desktop users.

My question is: anyone else faced same situation and found a solution or found a reason why its behaving?

Additional Information and Findings:

My application is based on .Net and i have disabled all the other scripting PHP, Perl etc on my production Server except .Net in IIS Server. I have got some more clue on this issue as well. We are using browserCaps.config and 51degrees to detect mobile devices and webcrawlers. So some where, detection is causing issue with Google mobile crawler. Treating mobile crawler as desktop browser.


  • Is there a specific question that you need help with??
    – closetnoc
    Mar 25, 2015 at 2:35
  • @closetnoc: sorry. Just added the question.
    – Jeyara
    Mar 25, 2015 at 2:39
  • Cool! I do not have an answer for you on this, but I like to help to set people up for better answers along the way. I have not dealt with your scenario. Sorry. But I suspect that others have and can help.
    – closetnoc
    Mar 25, 2015 at 2:45
  • I can confirm Google Mobile-Friendly Test will detect if you are dynamically changing content on the same URL, so the issue is with your set-up. Have you set the vary header to hint to Google you are dynamically changing content? developers.google.com/webmasters/mobile-sites/mobile-seo/…
    – Max
    Mar 25, 2015 at 7:53
  • @max: Thanks. But there is no change of content. Its just change of lay out. MFT just loads desktop version of the page instead mobile version.
    – Jeyara
    Mar 26, 2015 at 0:11

2 Answers 2


I am responding as answer as i managed to figure out what exactly was happening.

MFT and PageSpeed Test were using 2 different user agents. PageSpeed's mobile user agent was detected correctly by 51dgree but MFT. So based on, this and this i have updated code base to detect MFT user agent. Now it works fine.

In my opinion it is best to move towards responsive design rather having 2 separate themes or websites for mobile and desktop. It will trouble free in long term.


You might want to check every single .htaccess file on all the folders you have full access to. Its quite possible that a backdoor was created in the script that creates the theme and you were unaware of it until now, and this backdoor overwritten your .htaccess files.

You need to specifically check those files for lines that contain part of google's IP addresses and remove them. Mobile device detection shouldn't be determined by one's IP address.

Google runs a couple blocks of IP addresses. you may want to execute this in a command prompt:

ping google.com

Then you'll get an IP address which you can put in at the box on the top right at whois.com to find the ip address range for google.

If that doesn't fix the case, then you will have to check the code that's producing the pages to see if a fragment of code involes part of google's IP address causing the desktop page to be displayed.

If that doesn't work for you, then there may be something else installed on the server or even in apache that causes certain IP addresses such as google's to redirect specifically to the desktop website.

So try these things and see if you can get lucky.

  • Hi, Thanks for the answer. I have added more detail on the question. Our application is based on .Net
    – Jeyara
    Mar 25, 2015 at 5:10

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