Can someone explain how the Washington Post knows I'm visiting their site from Reddit?

[This is what I see](https://imgur.com/8O0vt2g) when I clicked a Washington Post link from Reddit.

The link doesn't contain identifying information in it (I can't post the link itself because of the subreddit filter but it was just [WP.com]/ opinions/2022/07/08/brett-kavanaugh-dinner-steakhouse-mortons-protest-satire/).

I have AdBlock, Privacy Badger, and ublockOrigin extensions enabled.

I was surprised because I've never seen this before. Thanks.

Edit: Thanks everyone. Looks like it's probably https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referer

privacy reddit the washington post washington washington post