Filtersone rule per line
What each line does
Read back, in plain English, what each line of your ad blocker filter actually blocks
Test a URL and the rules that match it turn green.
Page it loads on is the domain of the page requesting that URL (it drives $third-party and $domain=).
Matching here is a simplified model. A real extension also looks at request type and tab state, so results are not guaranteed identical.
Use it as a first check that a rule hits the URL you meant.
Nothing you enter is sent to a server.
The Adblock-style filters shared by uBlock Origin, AdGuard and Adblock Plus. It reads network rules (such as ||example.com^$third-party), element-hiding rules (example.com##.ad-banner), exception rules (lines starting with @@) and comments. Extension-specific syntax (AdGuard $$, uBlock scriptlet injection and the like) is flagged as "extension-specific" rather than being called invalid.
Yes. Enter an address and the tool shows which of your rules match it. Matching covers the address patterns (*, ^ and ||) plus the common options such as $domain and $third-party. A real extension looks at more conditions (request type, tab state), so the answer here is not guaranteed to be identical. Use it to check that a rule you wrote hits the URL you meant.
No. Parsing and matching happen entirely inside your browser. Nothing you type is sent to a server or stored. The page uses no external libraries.
Changing how pages look on your own device is generally fine, but it also thins the ad revenue that keeps many sites running. Consider allow-listing the sites you want to keep reading. Filters also break pages when written carelessly. This tool exists so you can read back, in plain language, what a rule you wrote actually blocks.