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An image, script, stylesheet, or other external resource referenced in your HTML returned an HTTP 307 (Temporary Redirect) status, and the W3C validator could not follow the redirect to retrieve the resource.

HTTP 307 means the server is temporarily redirecting the request to a different URL while preserving the original HTTP method. The validator attempts to fetch external resources to check them (for example, validating a linked stylesheet or verifying an image exists), but it does not always follow redirects successfully. This can happen when the resource URL points to a CDN, authentication gateway, or URL shortener that issues a temporary redirect.

Common causes:

• The href or src attribute points to a URL that redirects (e.g., a shortened URL or an old CDN endpoint).
• The server requires cookies, authentication headers, or specific request headers before serving the resource, and falls back to a 307 redirect.
• The resource has moved and the server is using a temporary redirect instead of serving the content directly.

The fix is to replace the URL with the final, direct URL that actually serves the resource. You can find this URL by following the redirect chain in your browser's developer tools (Network tab) or with a command line tool like curl -L -v.

If the redirect is outside your control (e.g., a third-party CDN), and the resource loads correctly in browsers, this validator warning may not indicate an actual problem for end users. The validator simply cannot reach the resource to inspect it.

HTML examples

Before: URL that triggers a 307 redirect

<linkrel="stylesheet"href="https://example.com/old-path/styles.css">

After: direct URL to the resource

<linkrel="stylesheet"href="https://cdn.example.com/styles/v2/styles.css">

To find the direct URL, run:

curl-I-Lhttps://example.com/old-path/styles.css

Look at the final Location header in the redirect chain and use that URL in your HTML.