Ad blockers and page speed: what actually gets faster
Blocking ads cuts far more than the adverts. Trackers, analytics and the scripts they load in turn often outweigh the page itself, especially on mobile data.
An advert on a web page is rarely a single picture. Behind it sits an auction that decides which advert to show, scripts that measure whether you saw it, trackers that record where you've been, and often more scripts loaded by those scripts. The visible banner is the smallest part.
That's why an ad blocker can make some sites feel dramatically quicker and others barely change. What speeds up depends on how much of the page was never really the page.
What a page is actually loading
You can see this for yourself. On a computer, open a news site, press F12 (or Cmd+Option+I on a Mac) to open the developer tools, choose the Network tab and reload the page. The count at the bottom shows how many separate requests were made and how much data was transferred.
Look at the domains in the list. Plenty won't belong to the site: ad exchanges, analytics, social widgets, video players and tag managers.
Try it again with your blocker switched on for that site. The difference in request count is usually the clearest demonstration of what's being cut.
What actually gets faster
Less data downloaded. Ad images, autoplay video and tracking scripts all cost data. On a capped mobile plan this is often the most tangible benefit.
Less work for your processor. Scripts have to be run, not just downloaded, which is why a heavy page can stutter while scrolling. Cutting them helps older phones and laptops most.
Fewer layout jumps. Adverts that load late push the text around as you read. With them blocked, the page settles faster.
Better battery life. Less processing and fewer network requests means less power, which adds up over a day of browsing on a phone.
What doesn't change
An ad blocker can't speed up the site's own content. If the server is slow to respond, the images are enormous or your connection is weak, blocking adverts won't fix it. Sites that serve their adverts from their own domain, or build them into the page, are harder to block and may show little difference.
The biggest gains are on news, recipe and free streaming sites, which tend to carry the most third-party code.
When a blocker slows things down
Checking requests against filter lists is quick, and the saving far outweighs the cost. Problems usually come from stacking:
- Several blocking extensions at once. They duplicate work and can conflict. One good blocker is enough.
- Dozens of extra filter lists. The defaults cover most needs. Adding every list available increases memory use for little gain.
- Broken pages. Occasionally a site's own features depend on a blocked script, so a button or video won't load. Pausing the blocker for that site is the usual fix.
If adverts still appear despite a blocker, the causes are covered in why ads still show with a blocker installed.
Built-in options worth turning on
You don't need an extension to get some of the benefit. Most browsers now block a good share of trackers themselves:
- Firefox: Settings, Privacy & Security, Enhanced Tracking Protection. "Strict" blocks more, at a small risk of breaking some sites.
- Safari: Settings, Privacy, with "Prevent cross-site tracking" on. Content blockers can be added from the App Store and enabled per site.
- Chrome and Edge: both offer tracking and privacy settings, and Edge has a "Strict" tracking prevention level. Extensions in Chrome now work within stricter rules on how they filter requests, which most mainstream blockers have adapted to.
DNS-level blocking, set up on a router or through a private DNS setting on your phone, is another route. It filters requests for the whole device, including apps, but it can't remove adverts served from the same domain as the content.
Whichever route you choose, remember that many free sites rely on advertising. Most blockers let you allow adverts on sites you want to support, and that's a reasonable balance for sites you read often.