I am using SharePoint Online and was referencing the MicrosoftAjax.js file via /_layouts/MicrosoftAjax.js for the past several weeks without issue. A week later and no changes to the system and it is now not working/can't be found when I try to browse to it. Where is MicrosoftAjax.js located within SharePoint Online? I don't want to use the CDN.

I've also noticed that I can open it from an on premises site via /_layouts/MicrosoftAjax.js

3 Answers 3


MicrosoftAjax.js file has been rolled back to where it was. The issue should be resolved now. A process has been working on to prevent it from happen again.


SharePoint 2013 (Online and on-prem) added a version number to the _layouts path. Try /_layouts/15/MicrosoftAjax.js

  • I tried that as well, but have the same issue... A missing file/404. Is there a feature that needs to be enabled to slow access?
    – Kode
    Jun 6, 2015 at 18:36
  • 1
    No, you can't add files to the system folders by activating a Feature. I checked my SharePoint Online tenant and MicrosoftAjax.js is there at /_layouts/15/MicrosoftAjax.js Jun 6, 2015 at 19:58
  • Odd. I will have to check again, as I don't understand what could have changed. Maybe something is affecting my tenant.
    – Kode
    Jun 6, 2015 at 22:12
  • I just tested another tenant and it is working fine. It must be my tenant.
    – Kode
    Jun 7, 2015 at 2:46
  • We just noticed this in our tenant as well. This file was there a week a ago. Our developer goes on vacation and he notices that it's no longer there when he returns. (!) Our tenant build information is: vti_encoding:SR|utf8-nl vti_buildversion:SR|16.0.4107.1212 (which can be seen here: /_vti_pvt/buildversion.cnf) Jun 7, 2015 at 17:03

After speaking with Microsoft, they decided to remove this core file without notification, as they believed it was not in a lot of use, when in reality it affects a lot of users/developers. They have promised a KB article and solution in the near future, but for immediate help, you can use the CDN or pull the down the hard script from the CDN:


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