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Entra External Id: Custom CSS is not working

Rojan Maharjan 0 Reputation points
2026-06-15T02:30:14.1133333+00:00

I’m currently working on configuring a custom branding theme for External ID in Microsoft Entra, and I’m running into some issues.

I created a new theme and configured all the visual elements, including:

  • Application of the theme to the app
  • Logo and banner logo
  • Favicon
  • Background image

When previewing the theme, all images and visual elements appear correctly, so that part seems to be working as expected.

However, I’m facing two problems:

  1. Custom CSS is not being applied
    • The CSS file uploads successfully without any errors
    • But none of the styles take effect in the preview experience
  2. Custom text changes are not reflected
    • I’ve added custom text as part of the branding configuration
    • These changes also do not appear in the preview

What’s confusing is that when I use the same CSS file and configuration with the standard Company Branding (default sign-in experience), everything works perfectly.

Any guidance, known issues, or workarounds to get custom CSS, custom text, and theming working correctly in External ID would be much appreciated. Thanks!

Microsoft Security | Microsoft Entra | Microsoft Entra External ID

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  1. Shubham Sharma 17,675 Reputation points Microsoft External Staff Moderator
    2026-06-15T04:18:09.3+00:00

    Hey Rojan, it turns out this is a known bug in the External ID branding engine where custom CSS (and localized text overrides) doesn’t automatically flow into all pages of the customer tenant sign-in preview. The Product Group has a fix in flight, but meanwhile you can get your CSS and custom text pulling through by using a language override file.

    Here’s the quick workaround:

    1. Host your CSS somewhere public (for example, in Azure Storage with a public blob URL).
    2. In the Entra portal, go to External ID → Branding → Company Branding.
    3. Select the Languages tab (or “Language customization”).
    4. Add or edit your English (1033) entry: • Upload a small JSON override file that looks like this: { 
      "customCssUrl": "https://<your-storage-account>.blob.core.windows.net/<path>/your.css",  

"boilerplateText": "Your custom footer text here",  

// add any other text overrides in JSON form
      } • Save and publish.
    5. Clear your browser cache (or open an incognito window) and hit Preview. You should now see your CSS styles and text changes applied across all pages.

    Behind the scenes, External ID branding only pulls in your CSS and strings when they’re referenced in a locale override. Once the PG rolling fix lands, just uploading CSS/text in the main “Layout” and “Header/Footer/Text” blades will work again without the JSON hack.

    Hope that gets your theme back on track!

    References:

    1. Customize neutral branding in your External ID tenant – https://learn.microsoft.com/entra/external-id/customers/how-to-customize-branding-customers
    2. Neutral/default External ID branding concepts – https://learn.microsoft.com/entra/external-id/customers/concept-branding-customers
    3. CSS template reference guide – https://learn.microsoft.com/entra/fundamentals/reference-company-branding-css-template

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  2. AI answer

    2026-06-15T02:30:34.91+00:00

    Custom CSS and custom text are supported in Microsoft Entra External ID branding, but they are applied and previewed only within the External ID branding/theming experience itself. The behavior can differ from the standard Company Branding (default sign-in experience) in a regular Entra ID tenant.

    From the provided information:

    • External ID tenants use a neutral default branding that can be customized with background image/color, favicon, layout, header, footer, and custom CSS.
    • Custom branding properties (including CSS) can be added individually, or a custom CSS file can be uploaded to override Microsoft defaults for color, font, text size, element positioning, and responsive behavior.
    • If custom company branding fails to load, the sign-in page reverts to the neutral branding.

    Given that the same CSS works in standard Company Branding but not in External ID:

    1. Confirm that the CSS is uploaded in the External ID theme itself (not only in the default company branding for the primary Entra ID tenant). External ID has its own branding surface.
    2. Use the Styling tab of the External ID theme to upload the CSS under Custom CSS and then use the Preview button for that theme. The preview for themes is driven by the theme’s own styling configuration (background, logos, favicon, and custom CSS) and is separate from the default company branding.
    3. Ensure that the preview being checked is the one for the External ID theme (created via the branding themes experience), not the default sign-in experience.
    4. If the sign-in page falls back to neutral branding (for example, if the custom branding fails to load), none of the custom CSS or custom text will appear. In that case, verify that the theme is correctly associated with the External ID application and that the theme is active.

    For custom text:

    • Custom text is configured on the Custom text tab of the theme, per page (Sign-in, Sign-up, Attribute collection). The preview must be for the same theme and page type to see the changes.
    • If the theme preview is not showing custom text, verify that the text was saved for the correct page (for example, Sign-in vs Sign-up) and that the preview is for that page.

    If all of the above are correct and the issue persists, this points to a product behavior specific to External ID theming rather than to the CSS file itself, since the same CSS works in standard company branding. In that case, the supported path is to continue using the External ID branding/theming surfaces (Styling + Custom text tabs) and, if the preview still does not reflect changes, open a support case so the backend configuration and loading of External ID themes can be checked.

    References:

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