Admin CSS MU – Load an Admin Side CSS For Customizing WP-Admin

Note: I have updated this plugin with an admin interface. You can read more about the plugin on the WordPress plugin directory. The following write-up applies to version 1.0 of the plugin. Download links are available at the end of the post.

If you want to add CSS on the login pages and front-end, in addition to the Admin side, use my Custom Login Admin Front-end CSS plugin. It supports multisites as well.


Admin CSS MUI had written on how to load CSS on the admin side before. This involved adding the load function into the functions.php of the theme.

Recently a need arose where the CSS had to be loaded irrespective of the theme being used, on a multisite network. So the function took shape as a plugin and I have my first WordPress plugin up in the extend.

Admin CSS MU

Admin CSS MU simply loads a CSS file. All your custom CSS can go into that file. I think the best use case for the plugin would be as a mu plugin, since it wouldn’t probably need an update ever (and hence the MU in the name).

Installation Instructions:

To use as a normal plugin in WordPress single install and Multisite.

  • Install the plugin through the WordPress admin interface, or upload the folder /admin-css-mu/ to wp-content/plugins/ using ftp.
  • Move (or create) custom_admin.css to wp-content/themes/ folder. (it should look like wp-content/themes/custom_admin.css)
  • Add the custom css you want into custom_admin.css.
  • Activate the plugin via WordPress admin interface. If it is a Multisite, preferably Network Activate it.

To use as a Must Use (mu) plugin for WordPress single install and Multisite.

  • If you don’t have already, create a folder /mu-plugins/ in /wp-content/ directory on your server. (it should look like wp-content/mu-plugins/)
  • Upload the file (just the file, not folder) admincssmu.php to wp-content/mu-plugins/ . (it should look like wp-content/mu-plugins/admincssmu.php)
  • Move (or create) custom_admin.css to wp-content/themes/ folder. (it should look like wp-content/themes/custom_admin.css)
  • No activation is necessary. MU plugins are always active and can only be deactivated if you delete it. No auto-updates are available though.

Plugin Page | Download Ver 1.0 | Download Latest | CSS Samples

Hope you find this useful. If you like it, please give it a 5 star rating. Enjoy.

Hey! Thanks for reading. If you found it useful, please share it with your friends as well. They will thank you for it.

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10 Comments.

  1. Karan says:

    This is great. Having your custom CSS file get uploaded is awesome. Thanks Arun, really helpful for our web designers team.

  2. Jungleads says:

    This was a great plugin really nice keep up your good work,please do develop more usefull plugins.

    Thanks again.

  3. chandan says:

    thanks a lot sharing this works well…

  4. Nazmul says:

    Oh! Nice plugin..thanks

  5. Lizee Helene says:

    worked well!!
    Thanks for sharing mate!

  6. George says:

    Did you made this plugin? That’s really cool. I would love to see more of your developed plugins.

  7. Maadhav Saxena says:

    Nice plug-in! Just added it and it works like a charm! Thanks

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