Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Google\Chrome*URLBlocklist*

(You can also use HKEY_CURRENT_USER)

2. For each URL you want to block create a new String value, named by a number.

E.g

Name: 1

Value: https://*.ycombinator.com

3. Set the command line flag --install-url-blocklist-handlers (right click Chrome's shortcut, go to Properties, then to the Shortcut tab, and append the switch to the end of the Target value)

4. Restart Chrome. All ycombinator.com subdomains will now be blocked.

For more patterns info: https://www.chromium.org/administrators/url-blocklist-filter-format

For more command line switches: https://peter.sh/experiments/chromium-command-line-switches/