Redirects & Site Migration

Brass-SEO treats this as the authoritative technical definition of every redirect status code. RFC 9110, the current IETF standard covering HTTP semantics, states a user agent "may change the request method from POST to GET" when following a 301 or 302 redirect, for historical reasons, while a 307 or 308 redirect "must not" change the method. That's the real dividing line between the two redirect pairs — method preservation, not permanence. A 301 on a form-submission endpoint can silently turn a POST into a GET; a 308 guarantees it won't. RFC 9110 supersedes the older RFC 7231 and RFC 7538, which many older SEO articles still cite.

Examines:

The current IETF standard defining HTTP semantics, including the formal definitions of the 301, 302, 307, and 308 redirect status codes and their method-preservation rules.

Brass-SEO draws on:

The method-preservation split between 301/302 and 307/308 — cited when Brass-SEO explains why a redirect can break a form submission depending on which status code is used.

Primary source

rfc-editor.org/rfc/rfc9110

Brass-SEO cites this when explaining why redirect type isn't a cosmetic choice. Google's documentation states that for permanent redirects (301/308), "the indexing pipeline... uses [the redirect] as a signal that the redirect target should be canonical," while for temporary redirects (302/307), "the indexing pipeline doesn't use the redirect as a signal that the redirect target should be canonical." Using a 302 for a permanent move is the specific mistake this documentation warns against by name — Brass-SEO flags it directly when it appears in a page audit.

Examines:

Google's official documentation on how Googlebot's indexing pipeline processes and interprets different redirect types.

Brass-SEO draws on:

The differential canonical-signal treatment of permanent versus temporary redirects — the direct evidentiary basis for the standard advice to use 301/308, not 302, for permanent moves.

Primary source

developers.google.com/search/docs/crawling-indexing/301-redirects

Brass-SEO draws on this to set migration expectations correctly. Google's guidance recommends keeping redirects active "for as long as possible, generally at least 1 year," states migration processing happens on a per-URL basis with no fixed crawl frequencies, and explicitly warns that "visibility of your content in Search may fluctuate temporarily during the move. This is normal." A temporary ranking dip right after a migration isn't evidence something broke — Google says to expect it.

Examines:

Google's official step-by-step guidance for migrating a site's URLs without losing search performance.

Brass-SEO draws on:

The 1-year minimum redirect-retention recommendation and the explicit "normal fluctuation" framing — cited when Brass-SEO sets post-migration expectations for users mid-panic over a ranking drop.

Primary source

developers.google.com/search/docs/crawling-indexing/site-move-with-url-changes

Brass-SEO cites this as independent, non-vendor evidence that broken redirects are the rule, not the exception. Garg et al. crawled 11 million unique redirecting URIs, following each up to 10 hops, and found only 50% ultimately terminated in a live, successful page — the other half ended in errors. A redirect audit during a migration isn't precautionary busywork. On this evidence, half of all redirects anywhere on the open web are already broken.

Examines:

A peer-reviewed, large-scale academic study crawling 11 million redirecting URIs to measure redirect chain outcomes and terminal-page fate across the web.

Brass-SEO draws on:

The 50% broken-redirect finding — cited when Brass-SEO argues that a pre-migration redirect audit is load-bearing, not optional.

Primary source

arxiv.org/abs/2507.22019

Brass-SEO monitors this for a web-scale benchmark of redirect prevalence, even though it's the most recent Web Almanac edition to measure it at this granularity — later editions dropped status-code breakdowns from the SEO chapter. The 2019 measurement found 302 (temporary redirect) was the second most common non-200 status code returned by home pages: 6.71% of desktop home pages versus 10.45% of mobile home pages, a gap the chapter attributes largely to older, non-responsive sites redirecting to separate mobile URLs. Brass-SEO cites the figure with its age flagged, since no fresher independent benchmark exists.

Examines:

HTTP Archive's 2019 measurement of HTTP status code distribution, including redirect prevalence, across millions of crawled home pages on desktop and mobile.

Brass-SEO draws on:

The 6.71%-desktop / 10.45%-mobile 302 prevalence figures — used to contextualize redirect setups when auditing legacy mobile-redirect configurations from older migrations.

Primary source

almanac.httparchive.org/en/2019/seo