- Redirect
- A mechanism where the server returns a 3xx status code and Location response header, instructing the client to automatically visit another URL. Redirects are usually transparent to the user, and browsers automatically follow jumps.
- 301 Moved Permanently
- Permanent redirect status code. Indicates the resource has permanently moved to a new location. Search engines transfer the old URL's PageRank to the new URL, and browsers cache this redirect long-term. Recommended for permanent changes like domain migration and HTTPS switching in GET request scenarios.
- 302 Found
- Temporary redirect status code (formerly Moved Temporarily). Indicates the resource is temporarily located elsewhere. Search engines do not transfer authority, and browsers don't cache long-term. Note: most browsers convert POST requests to GET when receiving 302, potentially losing the request body.
- 303 See Other
- See Other status code. Typically used for redirecting to a result page after POST form submission, explicitly requiring the client to request the new URL via GET to prevent duplicate form submissions. 303 responses should not be cached.
- 307 Temporary Redirect
- Temporary redirect status code (introduced in HTTP/1.1). Same semantics as 302, but strictly requires preserving the request method and body—POST requests receiving 307 must still request the new URL as POST, without losing form data. Suitable for temporary redirects in API and form scenarios.
- 308 Permanent Redirect
- Permanent redirect status code (defined in RFC 7538). Same semantics as 301, but strictly requires preserving the request method and body—POST requests receiving 308 still redirect as POST. It's the "method-safe" version of 301, fully supported by modern browsers.
- Location header
- HTTP response header field used to specify the target URL in 3xx redirect responses. Can be an absolute URL (recommended) or relative URL. The client automatically initiates a new request to that URL after receiving it. Non-ASCII characters in Location headers must be URL-encoded.
- Redirect Chain
- A series of consecutive redirects from the initial URL to the final destination URL. For example, A→B→C→D forms a 3-hop redirect chain. Excessively long redirect chains slow down loading speed and erode SEO authority—recommended to keep to a single hop, no more than 3 maximum.
- Redirect Loop
- When a URL repeats in the redirect chain, forming an infinite jump cycle (like A→B→A). Browsers display ERR_TOO_MANY_REDIRECTS errors after reaching the maximum redirect count (usually 20). Common causes include HTTP↔HTTPS mutual jumps, www↔non-www mutual jumps, and reverse proxy protocol loss.
- Domain Migration
- The process of permanently switching a website from one domain to another, such as brand renaming or company mergers. During migration, all URLs on the old domain need to be 301-redirected to corresponding pages on the new domain, and a domain change notification should be submitted in Google Search Console.
- URL Canonicalization
- The process of unifying multiple URL variants of the same content (www/non-www, with/without trailing slash, HTTP/HTTPS, case differences) into a single standard URL, typically implemented via 301 redirects. Canonicalization avoids duplicate content issues and concentrates SEO authority.
- HTTPS Forced Redirect
- Configuration that redirects all HTTP (port 80) requests to HTTPS (port 443) via 301 redirects. It's a necessary step after deploying SSL/TLS certificates. Typically used with HSTS response headers to eliminate the HTTP plaintext window on first visit.
- HSTS
- HTTP Strict Transport Security—via the Strict-Transport-Security response header, tells the browser to only access the domain via HTTPS within a specified time. The browser internally automatically upgrades HTTP to HTTPS without server redirect. Effectively defends against SSL stripping attacks.
- Short URL
- Services that convert long URLs to short URLs (like bit.ly). Accessed via 301/302 redirects jumping to the original URL. Short URLs often hide multi-hop redirect chains behind them, potentially containing tracking parameters or redirecting to different targets under certain conditions.
- PageRank
- Web page ranking algorithm invented by Google founders Larry Page and Sergey Brin, evaluating page authority through link relationships. 301 permanent redirects transfer the old URL's PageRank to the new URL, while 302 temporary redirects typically transfer none or very little.
- Core Web Vitals
- Core web experience metrics defined by Google, including LCP (Largest Contentful Paint, measures load performance, good threshold ≤2.5s), FID/INP (interactivity, good threshold ≤100ms/200ms), and CLS (visual stability, good threshold ≤0.1). Redirect chains delay HTML download and directly worsen LCP metrics.
- Cross-origin Redirect
- When the redirect target URL has a different domain than the original URL (including completely different domains or different subdomains). Cross-origin redirects are constrained by the same-origin policy, potentially causing Cookies not to be sent, third-party Cookie blocking, and CORS preflight failures.
- Chain Truncation
- When the number of redirect chain hops exceeds the maximum depth limit set by the tool or browser (20 hops for this tool, 20 for Chrome), the tracer stops following subsequent redirects and marks the chain as truncated. Chain truncation usually suggests an infinite loop or abnormally complex redirect configuration.
