When your users open email messages, Gmail uses Google’s secure proxy servers to serve images that might be included in these messages. This protects your users and domain against image-based security vulnerabilities.
Because of the image proxy, links to images that are dependent on internal IPs and sometimes cookies are broken. The Image URL proxy allowlist setting lets you avoid broken links to images by creating and maintaining a allowlist of internal URLs that'll bypass proxy protection.
When you configure the Image URL proxy allowlist, you can specify a set of domains and a path prefix that can be used to specify large groups of URLs. See the guidelines below for examples.
Configure the Image URL proxy allowlist setting
In the Admin console, go to Menu AppsGoogle WorkspaceGmailEnd User Access.
- On the left, select your top-level organization.
- Scroll to the Image URL proxy allowlist section.
- Enter image URL proxy allowlist patterns. Matching URLs will bypass image proxy protection. See the guidelines below for more details and instructions.
- At the bottom, click Save.
You can track prior changes under Admin console audit log.
Guidelines for applying the Image URL proxy allowlist setting
Consult with your security team before configuring the Image URL proxy allowlist setting. The decision to bypass image proxy allowlist protection can expose your users and domain to security risks if not used with care.
In general, if you have a domain that needs authentication via cookie, and if that domain is controlled by an administrator within your organization and is completely trusted, then allowlisting that URL should not expose your domain to image-based attacks.
Entering Image URL patterns
To maintain an allowlist of internal URLs that'll bypass proxy protection, enter the image URL patterns in the Image URL proxy allowlist setting. Matching URLs will bypass the image proxy.
A pattern can contain the scheme, the domain, and a path. The pattern must always have a forward slash (/) present between the domain and path. If the URL pattern specifies a scheme, then the scheme and the domain must fully match. Otherwise, the domain can partially match the URL suffix. For example, the pattern /google.com matches www.google.com, but not gle.com. The URL pattern can specify a path that's matched against the path prefix.
- Enter your actual domain name as you enter the image URL pattern.
- Always include a trailing forward slash (/) after the domain name.
Examples of Image URL pattern
The following patterns are examples only.
The following patterns:
... will match the following URLs:
Note: The URL scheme (http://) is optional. If the scheme is omitted, the pattern can match any scheme, and allows partial matches on the domain suffix.
Previewing the image URL patterns
Click Preview to see if the URLs match the image URL patterns you've set. If the image URL matches a pattern, you'll see a confirmation message. If the image URL does not match, an error message appears.