Does Googlebot Use Etag Headers?

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Source: https://tamethebots.com/blog-n-bits/does-googlebot-use-etags

Conditional requests in plain terms

HTTP has a built in way to avoid resending content that has not changed. When a server first serves a page it can include an ETag header, which is a fingerprint of that version of the resource, and a Last Modified header with a timestamp. On a later visit the client sends those values back in an If None Match or If Modified Since header. If nothing changed, the server replies 304 Not Modified with no body, and the client reuses what it already had. This is standard caching behaviour, and Googlebot participates in it.

What the testing found

Practical testing of Googlebot traffic shows it does send these validators on revisits and does act on a 304 response by treating the stored version as current. That matters for crawl efficiency: a 304 costs your server almost nothing to produce and saves Googlebot from downloading a full response it already has. Across a large site with many stable pages, that saved effort can be redirected toward the URLs that changed, which ties directly to how crawl budget works.

How to check your own responses

You can inspect the headers yourself. Request the page and look at the response headers to confirm an ETag or Last Modified value is present:

curl -sSI "https://example.com/page/"

Then repeat the request while sending the value back, and confirm the server answers 304 rather than 200:

curl -sS -o /dev/null -w "%{http_code}\n" \
  -H 'If-None-Match: "the-etag-value-here"' \
  "https://example.com/page/"

If you get a 200 with a full body even though nothing changed, your stack is not honouring validators, and you are giving up an easy crawl efficiency win.

Getting it right

Emit a strong, stable ETag that only changes when the content changes, and keep Last Modified accurate. Avoid tying the ETag to values that shift on every request, such as a timestamp or a per request identifier, because that defeats the purpose and forces a full fetch every time. Many CDNs and application servers handle this automatically for static assets, but dynamic pages often need explicit configuration. The rendering and fetching theme also connects to how pages are composed and fetched.

Validators and responses at a glance

What has changed since this case study

Google has been increasingly explicit that supporting HTTP caching and conditional requests helps crawling. Its crawl budget guidance now calls out that serving 304 responses for unchanged content is a legitimate way to make crawling more efficient, which lines up with what independent testing observed. Nothing about the underlying HTTP mechanism has changed, because ETag and Last Modified are long standing standards. What has shifted is the emphasis: as sites grow and Google pushes for crawl efficiency, correctly implemented validators have moved from a nice to have to a practical lever for large sites.

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