Disabling the "Enable notifications?" popup in Firefox

If I'm on a page that has web notifications (like Slack or others), Firefox asks me if I want to enable them. However, my choices are "Yes" or "Ignore for now". The problem is, if I select "Ignore", every time there is a notification it asks me again. This is incredibly annoying.

How do I disable this completely? (I would accept disabling this feature entirely if that's easiest.)

Go into about:config and set dom.webnotifications.enabled to false

You can also disable this on a per-site basis by right-clicking somewhere in a blank spot of the site (or pressing Ctrl-I on Windows or Cmd-I on Mac) and then selecting "View Page Info" from the opening menu. This opens a window with a "Permissions" tab. Scroll down until you see "Receive Notifications", uncheck "Use Default" then select "Block."

Go into about:config and set dom.webnotifications.enabled to false. This seems to work for me in FF 47.

As of Firefox 59, this is in Options

Open the Options window

On the left side of the screen, click "Privacy & Security"

Under the "Permissions" section, find "Notifications" and click the "Settings..." button

Check the box that says "Block new requests asking to allow notifications"

In about:config I set dom.webnotifications.enabled to false but it didn't work for me in FF 56. I had to set dom.push.enabled to false as well.