A disavow file is a plain-text file submitted to Google via Search Console that instructs Google to ignore specified backlinks when assessing a site’s link profile. Each line lists either a specific URL or an entire domain to disavow, prefixed with domain:. The tool was introduced in 2012 in response to widespread link-based penalties following the Penguin update. Google’s own guidance is to use it only when you have a significant number of spammy or artificial links that you cannot remove through direct outreach, and where you have reason to believe those links are causing or risking a manual action. Casual or pre-emptive disavowal of ordinary links is not recommended. The file is processed over weeks, not immediately.