Short answer: they're wrong. The confusion happens because people mix up three very different things. I'll explain it here.

First, the internet has three layers, and most people confuse them:

Surface Web: indexed by search engines, publicly accessible

Deep Web: not indexed, but not hidden (think: your email inbox, bank portal, private databases)

Dark Web: intentionally hidden and requires special software like Tor or I2P to access

The 80% claim actually refers to the Deep Web, not the Dark Web. These are not the same thing.

https://x.com/T3chFalcon/status/2054109454832914443

Where does the 80% (or 90%, or 96%) figure come from?

It traces back to a 2001 study by Michael Bergman, who estimated that the "deep web" was 400-550x larger than the surface web at the time.

Media outlets picked up the story. Over time, people started confusing "deep web" with "dark web" in pop culture, and that's how the myth started.