Links are fundamental to SEO. Internal links distribute PageRank, external links show authority, and link attributes (nofollow, sponsored) signal relationship types. Analyzing link structure reveals optimization opportunities.
Internal vs External Links
Internal links point within the same domain—they help users navigate and distribute SEO authority across pages. External links point to other domains—they show topic relationships and can pass authority. A healthy site has good internal linking (no orphan pages) and selective external linking to reputable sources. Link scrapers count both types for site audits.
Link Attributes and SEO
rel="nofollow" tells search engines not to pass authority through the link. Use for user-generated content, paid links, or untrusted sites. rel="sponsored" explicitly marks paid links. rel="ugc" marks user-generated content. Links without these attributes are "dofollow" and pass authority. Analyzing link attributes reveals how a site manages PageRank flow.
Broken Link Detection
Broken links (404 errors) harm user experience and SEO. Link scrapers extract all URLs, then check HTTP status codes. Internal broken links should be fixed immediately. External broken links to authoritative content should be updated to archived versions or alternatives. Regular broken link audits maintain site health.