What is Canonical Tag?
A hint (rel="canonical") naming the preferred URL when duplicates exist. Only about three in five pages web-wide carry a valid one, so validation must cover target quality and conflicting signals.
Example
A product reachable at /p/123, /sale/p/123, and /p/123?ref=x carries one canonical to /p/123. All three remain crawlable, but signals consolidate on the preferred URL.
What people get wrong
Pointing canonicals at broken or redirected URLs. The consolidation signal then aims at a page that cannot resolve, which is worse than no canonical at all.
Related terms
Duplicate Content
Substantively identical content at multiple URLs, from facets, parameters, or syndication. Diagnose the pattern (template, locale, pagination) before prescribing canonicals or consolidation.
301 Redirect
A permanent redirect passing most ranking signals to the target URL. Use it for migrations, consolidation, and retired pages with a live equivalent.
Pagination
Splitting long listings across numbered pages. Each page needs intentional canonical behavior and crawlable next/prev paths so deep items stay discoverable without duplicating signals.
Technical SEO
The crawling, indexing, rendering, and performance work that lets search engines reach, understand, and serve your pages. It covers directives, architecture, speed, and structured data rather than words on the page.
Crawling
How search-engine bots discover pages by following links, sitemaps, and directives. If a URL is never crawled, it cannot be indexed no matter how good its content is.
Crawl Budget
The number of pages a search engine will crawl on a site in a given period, driven by server capacity and demand signals. Large or slow sites must spend it on indexable, valuable URLs.