HTTP Header Auditor

The headers your pages send shape how efficiently crawlers work through your site. This audits them live, and it actually tests whether conditional revalidation gets you a 304.

The efficiency layer nobody looks at

Googlebot revalidates aggressively. If your server handles conditional requests properly, recrawling an unchanged page costs a tiny 304 instead of a full download, and sites that get this right get recrawled more per unit of crawl budget. Most header tools just print your ETag back at you. This one replays it in a second request and reports what your server actually did, because a surprising number of stacks emit validators and then ignore them. Dynamic pages that regenerate the ETag on every request are the usual culprit.

What it audits

  • Revalidation, tested for real. ETag or Last-Modified present, conditional GET sent, did a 304 come back?
  • Compression: Brotli, zstd, gzip, or nothing at all on your HTML
  • Cache-Control sanity for HTML documents
  • Vary pitfalls, specifically Vary: User-Agent, which splits your cache and hints at UA-based serving, and Vary: *
  • X-Robots-Tag surprises. A header-level noindex never shows up in view-source, and it has deindexed entire sites.
  • Link headers, where canonicals and hreflang can hide from every on-page audit you run
  • Content-Type and charset, HSTS, and whatever your CDN reveals about cache HIT and MISS status

The tool makes two requests: a normal GET, then a conditional GET replaying your ETag or Last-Modified to test revalidation for real. Headers are read from Cloudflare's edge, so a CDN sitting in front of your origin may be answering some of them. Nothing is stored.