Hidden links are backlinks or internal links deliberately made invisible to a visitor, most classically by setting the link text's color to exactly match the background, while remaining fully present and readable in the page's actual HTML for a crawler to find. Other variations include shrinking link text to an unreadable size, positioning it off-screen, or burying it behind another element.
The tactic dates back to when search engines mostly read raw HTML without much ability to judge how a page actually rendered visually, so a link invisible to a human reader still counted the same as any other link to the crawler reading the code. That gap closed a long time ago: modern crawlers render pages much closer to how a real browser does, which makes hidden links straightforward to detect by comparing what's visible against what's technically present in the markup. Any site that inherited hidden links from an old SEO vendor, or discovers them during a site audit, should remove them outright rather than leave them in place, since the risk they carry today is entirely downside with none of the ranking benefit the old tactic once claimed to offer.
