Rewrite vs redirect

A redirect answers with a status code and a Location header, so the browser makes a second request and the address bar changes. 301 and 308 are permanent and act as a strong canonicalization signal, so search engines consolidate ranking on the new URL. 302 and 307 are temporary and generally leave the original URL as the canonical one, though a temporary redirect left in place for months can end up treated like a permanent one. A rewrite is invisible: one request, the server maps the path to different content behind the scenes, and the URL the visitor sees never moves.

Redirect when the canonical address genuinely changed: renamed pages, www to apex, http to https, retired campaign URLs. Rewrite when the address is the product and the source is an implementation detail: '/blog' served from a separate CMS deployment, '/docs' proxied from another origin, a customer subdomain mapped to '/tenants/acme'.

Gotchas worth the scar tissue. A 301 gets cached hard by browsers and is close to impossible to take back, so use 307 while you are still experimenting. Rewrites can leave the same page reachable at two URLs, which splits SEO signals unless you set a canonical tag. And relative asset paths often break behind a rewrite, because the browser resolves them against the URL it can see, not the one you rewrote to.