blog: Don Marti


browser.fastblock.timeout and browser.fastblock.limit

22 September 2018

(update 24 Sep 2018: add link to a FastBlock description on Bugzilla)

What's the difference between Firefox browser.fastblock.timeout and browser.fastblock.limit?

  • browser.fastblock.timeout: When Fastblock starts working (in milliseconds, default 5000 = 5s)

  • browser.fastblock.limit: When Fastblock stops working (also in ms, default 20000 = 20s).

FastBlock only works if browser.contentblocking.enabled and browser.fastblock.enabled are both true.

Starting browser.fastblock.timeout ms after the page starts loading, FastBlock will stop loading new third-party resources that are on the Tracking Protection list.

  • FastBlock does not affect third parties that are not on the Tracking Protection list.

  • FastBlock does not cancel third-party requests that are already loading.

Then, starting at browser.fastblock.limit ms after the page starts loading, FastBlock stops having any effect.

More on Fastblock here

The sole focus of the Fastblock feature is to restrict the loading of trackers. It monitors trackers waiting for the first byte of data since the start of navigation of the current tab’s top level document. If this is not received within 5s, the request is canceled. If any bytes are received, the 5s timer is stopped. In some of the experimental branches, a few tracker requests are whitelisted, and do not have this monitoring. These include resources known to cause breakage, such essential audio/video, and commenting platforms.

Here's the code.

Fastblock plus European mode

Just going by basic economics, ads placed with more information about me are going to carry less signal and more deception than ads placed only by what page they're on. Now I'm wondering how well "slow loading ads" correlate with "deceptive ads". Are slow loading ads slow because they depend on a bunch of complex RTB stuff? Can less creepy ads be faster?

By combining FastBlock with a brower extension to turn on Google's documented but underrated European mode, I should be able to get a better class of web ads all around. I'll give it a try and follow up with how it goes.

This post is a work in progress. I'll update as needed to fix errors and update with current browser behavior.