1. The “Sitewide Link” Illusion

The most common reason for a massive drop (e.g., losing 5,000 links overnight) is the removal of a single Sitewide Link.

If a web designer puts “Designed by [Agency]” in the footer of a client’s website, that single link appears on every page of the client’s site. If the client has 5,000 pages, you have 5,000 backlinks. If they redesign their site and remove that one footer credit, your backlink count drops by 5,000 instantly.

Check your Referring Domains count. If “Total Backlinks” dropped by 5,000 but “Referring Domains” only dropped by 1, this is the cause. It is rarely a SEO problem because Google typically counts sitewide links as one single vote anyway.

2. Tool Index Updates (Ahrefs/Semrush)

It is crucial to remember that third-party tools (like Moz, Ahrefs, or Semrush) are not Google. They have their own crawlers and databases.

Periodically, these tools “clean” their index to save space. They might remove low-quality links, spammy directories, or very old pages that haven’t been visited in years. A drop in your Moz DA or Ahrefs Backlink count often just means the tool updated its database, not that you actually lost valuable links in Google’s real index.

Log into Google Search Console > Links. This is the only “source of truth.” If the links are still there, the drop in your SEO tool is irrelevant.

3. The “Dead Page” (404) Issue

Links exist on pages. If the owner of the linking website deletes a blog post, or if their entire website goes offline (expires), the link dies with it.

This is common with “Link Rot.” Over time, the web decays. If you built links on low-quality directories or forums five years ago, it is highly likely those sites no longer exist today.

Use the “Lost Links” report in your SEO tool. Look at the Target URL. If the status code of the linking page is “404 Not Found” or “DNS Error,” the site is gone. You cannot fix this unless you contact the site owner (if they still exist) and ask them to reinstate the content.

4. Google’s “Link Spam” Updates

Google frequently rolls out Link Spam Updates. When this happens, Google’s AI (SpamBrain) nullifies spammy links.

While this doesn’t strictly “delete” the link from the web, it effectively makes the link count for zero in Google’s ranking algorithm. If you bought links or participated in link schemes, and your rankings drop alongside your backlink count, this is likely a manual or algorithmic penalty devaluing those assets.

Check the Manual Actions tab in Google Search Console. If you see “Unnatural links to your site,” you have been penalized. If there is no message, it might be an algorithmic devaluation (which sends no notification).