This is merely about the URL you want to block. This can be the full URL to only block one specific file or only block files on a specific path or block everything from a server. You can possibly drag a specific request to the "block resource when the URL contains" bar and then remove trailing text until you are satisfied.

You didnt read my question. I asked about patterns. For example how do I block every request that goes to let's say any subdomain of google.com (but not google.com itself)?

Or other example, how do I block any request? For example I dont know in advance what url/uri will be posted when I click submit button. I want to click button anyways to see request it makes but I dont want server to get that request.

So the question is how do I write patterns? Does it use regex? Does it have some custom syntax?

Any example patterns?

I don't think that there is any pattern supported like you mean.

• https://searchfox.org/mozilla-release/source/devtools/client/netmonitor/src/utils/request-blocking.js
• https://searchfox.org/mozilla-release/source/devtools/client/netmonitor/src/components/request-blocking/RequestBlockingPanel.js

You can check the action on the form in the inspector to see what request will be send and block that URL.

I cant accept it as answer. The text in devtools says "Start by adding a pattern or dragging a row from the network table"

It has word pattern.

I cant accept it as answer. The text in devtools says "Start by adding a pattern or dragging a row from the network table"

It has word pattern.

Also the simplest pattern that blocks everything is *. This already proves that there is at least 1 pattern.