A 'toxic backlink' is industry shorthand for a link from a site that fits one or more of these patterns: thin or auto-generated content, irrelevant topical context, paid link networks (PBNs), comment-spam pages, scraper sites, or sites with their own manual penalties. Google's 2024+ algorithmic systems have become quite good at simply discounting these links rather than penalizing the recipient — so most toxic links require no action from you. The disavow tool is appropriate in three specific situations: (1) you have received a manual action from Google for unnatural links and need to disavow before reconsideration; (2) you have strong evidence of a coordinated negative SEO attack with thousands of new spammy links pointing at your site; (3) you have inherited a site from a previous owner who actively bought spammy links and you need to clean the slate. For everyone else, the safest action is no action — disavowing legitimate links is more dangerous than leaving toxic ones alone.