“Additional CSS” is a feature from WordPress core that was first introduced on WordPress 4.7.
This feature was initially created to make it easier for users to customize their site's CSS without the need for additional plugins or directly editing their theme.
You can normally find this feature by navigating to Appearance -> Customize -> Additional CSS.
When you make CSS changes in the “Additional CSS”, they will be reflected in the Customizer preview. This allows you to refine the appearance of your website without actually implementing any changes until you are satisfied with the overall result.
However, in some situations, the “Additional CSS” tab is missing in the customizer. Here are a few reasons why it happens:
#1. Plugin Conflict
The first reason why the “Additional CSS” tab may be missing is a plugin conflict. You can check whether or not this is a plugin conflict by temporarily disabling all of your plugins and seeing if the “Additional CSS” tab is back.
#2. Multisite Environment
This is because multisite networks in WordPress are open networks that are encouraged to take greater precautions. So for security reasons, WordPress only allows Super Admins to change the site's CSS.
#3. Missing “unfiltered_html” capability
The last reason why the “Additional CSS” tab may be missing is that your user role does not have the unfiltered_html capability. The unfiltered_html capability could be very dangerous in the wrong hands, that’s why WordPress does not give this permission by default to all of the roles.
If this is the case, you can easily add the unfitered_html capability by using the PublishPress Capabilities plugin.
- Install and activate PublishPress Capabilities
- Go to the “Capabilities” menu in the left WordPress admin panel.
- Select the role in the top left and click the “Admin” tab.
- Check the “unfiltered html” box.
- Click “Save Changes”.
Now you can utilize the User Testing feature to see if the Additional CSS tab is showing.