Missing ETag header: enable conditional GET

What it means

The HTTP response for this page includes no ETag header. An ETag is a content fingerprint (typically a body hash) that lets clients revalidate a page with a conditional If-None-Match request. With neither an ETag nor a Last-Modified header, this page has no cache-revalidation mechanism at all.

Why it matters

ETag and Last-Modified serve the same crawl-efficiency purpose — one by hash, one by timestamp. Either enables conditional GET: the crawler sends its stored validator and the server replies 304 Not Modified (no body) or a full 200. When both are absent the full body transfers on every crawl visit. ETag has an edge for dynamic content because it can be based on a hash of the output even when a page is regenerated per request. This is a lab-proxy from the response headers, reported as a notice.

How to fix it

1. On Apache, FileETag generates ETags for static files by default; on Nginx they are automatic for static files.
2. For dynamic responses, generate a hash from content-relevant data (e.g. record updated_at plus a version counter) and set it as the ETag, wrapped in double quotes per RFC 7232.
3. Verify your CDN (Cloudflare/Fastly/CloudFront) passes through or generates ETags rather than stripping them.
4. If implementing both headers is impractical, ship whichever is cheaper — either alone enables conditional GET.

When it's not a problem

Pages that must not be cached — real-time dashboards, payment pages, authenticated session content — should not expose ETags. A page already serving an accurate Last-Modified has an equivalent revalidation mechanism (Crawlinx reports the two independently). If a CDN sets its own ETag on the cached response Googlebot receives, the origin omitting it matters less — verify the header on the response Googlebot actually gets.

How common is it?

9845 audited sites in our corpus currently show this issue. The breakdowns below show which platforms, gatekeepers, verticals and countries are most exposed.