HTTP Header Auditor

The headers your pages send shape how efficiently crawlers treat your site. This audits them live — including actually testing whether conditional revalidation returns 304s.

The invisible efficiency layer

Googlebot revalidates aggressively: if your server supports conditional requests, a recrawl of an unchanged page costs a tiny 304 instead of a full download. Sites that get this right get recrawled more per unit of crawl budget. Most header tools just list your ETag — this one replays it in a second request and reports what your server actually did, because a shocking number of stacks emit validators and then ignore them (dynamic pages that regenerate ETags per request are the usual culprit).

What it audits

  • Revalidation, tested live: ETag / Last-Modified present → conditional GET → did a 304 come back?
  • Compression: Brotli, zstd, gzip, or nothing on your HTML
  • Cache-Control sanity for HTML documents
  • Vary pitfalls: Vary: User-Agent (cache-splitting, and a hint of UA-based serving) and Vary: *
  • X-Robots-Tag surprises — a header-level noindex is invisible in view-source and has deindexed entire sites
  • Link headers — canonicals and hreflang served at the header level that most on-page audits never see
  • Content-Type / charset, HSTS, and what your CDN reveals (cache HIT/MISS status)

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