Each backlink index runs its own crawler and sees a different subset of links. Ahrefs 2,069 (https://ahrefs.com/ 2,069 ) costs $129/month (free Ahrefs Webmaster Tools 2,069 for your own sites), Majestic 17,500 $49.99/month and LinkResearchTools 175,058 from $5,799/year; Whitespark 114,537 handles local citations, and Seobility 54,299 and OpenLinkProfiler 389,801 offer free checkers. Backlink Builder's site is blank. See External Backlink Factors for which links help.