Disavow
Disavowing is a Search Console request asking Google to ignore specific backlinks pointing at your site. It is a last resort for spam links you cannot get removed, and Google now says most sites should never need to use the tool at all.
Why it matters for your rankings
Disavow was essential after the Penguin updates of the early 2010s, when bad links could actively demote a site. Modern Google mostly ignores obvious spam rather than punishing you for it, so the tool matters far less than its reputation suggests.
It is also genuinely dangerous. The file is applied without confirmation, and disavowing legitimate links removes real ranking value that took years to earn. Agencies still sell routine disavow work, and cases of sites damaged by over-zealous files are more common than cases helped by them. The narrow situation where it earns its place is a manual action for unnatural links, or a known history of bought links you cannot get taken down. Outside that, leave it alone.
How to check it on your site
Check for a manual action first
Open Security & Manual Actions in Search Console. Without an unnatural links penalty, disavowing is usually unnecessary.
Export and review by domain
Pull referring domains from Ahrefs or Search Console. Judge at domain level, not link level, and only flag sites that are clearly spam networks or hacked.
Attempt removal first
Google expects genuine removal effort. Contact webmasters and document it before uploading anything.
Upload conservatively
Use domain: entries for whole spam domains, keep the file small, and never include a site you are unsure about.