Blocking website adverts in web browsers has been a hot topic in recent years and there are merits to both sides of the argument. Many sites out there bombard you with tons of ads, and quite often you will feel that you have no choice but to use an ad blocker because either the ads slow down the site loading too much, or they are incredibly annoying and get in the way or distract from your browsing.

On the other side, there are sites that try to inconvenience you as little as possible and be sensible with the amount of ads displayed and their placement. Blanket use of ad blockers will hurt those sites just as much as the bad sites you feel have gone overboard with their ads. It’s no secret the vast majority of websites on the internet need to use ads to help pay for running costs. Staff, hardware, fast servers, fast CDNs and the like are not free and need to be paid for.

But we cannot get away from the fact an ad blocker is probably the number one add-on for browsers like Chrome and Firefox, and will continue to be so for some time yet. Besides removing the adverts, ad blockers also save bandwidth by cutting down the amount of content a page loads, they can also help with your privacy by blocking scripts that track your browsing habits.

The Ad Blockers on Test

There’s several ad blocking extensions available for Chrome and Firefox, and some work better than others. To see what they do when when loading a web page, we’ve decided to put a number of ad blockers to the test. This test is about the performance of an ad blocker in terms of how quickly it loads a range of ad blocked pages, the maximum amount of memory it uses and how much stress it puts on the CPU.

There are many more ad blockers available in Chrome than in Firefox which is the reverse of what we expected. Here are the ones we are testing for both browsers.

AdBlock for Chrome – The most popular ad blocker for Chrome with reportedly over 200 million downloads. There was a Firefox version released briefly but that was pulled from the Firefox add on pages for unknown reasons. AdBlock has acceptable ad options for YouTube and Google search but they are off by default.

AdBlock Plus for Chrome/AdBlock Plus for Firefox – One of the most well known ad blockers and also one of the most controversial because AdBlock Plus started off the trend of introducing acceptable ad whitelists. The AdBlock Plus website also has versions for Opera, Safari, Maxthon, Internet Explorer and even Android.

AdBlock Pro for Chrome – AdBlock Pro is based on AdBlock Plus but has a simpler options interface and no acceptable ads option. The icon button sits in the address bar instead of the normal add on area and has 3 simple options to disable, go to options or create a filter.

Adguard for Chrome/Adguard for Firefox – Adguard is easy to use and extra blocking scripts can easily be added. Adguard’s main product is a shareware desktop application that blocks ads in a number of browsers without the need for browser add-ons. Beta versions of both add-ons are available for testers.

AdRemover for Chrome – AdRemover is based on AdBlock with just about the same number of options minus the support tab. On the face of it, most of the differences appear to be cosmetic and although it doesn’t ask for donations, there are social media buttons when clicking the icon.

Ghostery for Chrome/Ghostery for Firefox – Ghostery can block analytic scripts, widgets, web beacons, privacy scripts and or course advertisements. The good thing about Ghostery is the ability to individually enable or disable scripts on a per site basis. Versions are available for Opera, IE, Safari and mobile operating systems.

Simply Block Ads! for Chrome – This hasn’t been updated since 2014 and there’s reports that some ads aren’t being blocked, but it blocked all ads on our test sites so we included it. Simply Block Ads! (aka Simple Adblock) is the easiest to use and the only option is an opt-in to send usage statistics.

SuperBlock AdBlocker for Chrome – This is another AdBlock fork and appears to be by the same developer as AdRemover. Apart from an extra entry in the filter list and a few styling changes, we can’t see much difference between the two, perhaps there are more changes underneath.

µ Adblock for Firefox – µ Adblock (Micro Adblock) is Easylist and EasyPrivacy based, and almost as easy as it gets. Simply click the icon to block/unblock specific sites. There are only 3 options including blocking social buttons. One issue is µ Adblock hasn’t been updated since January 2015.

µBlock Origin for Chrome/µBlock Origin for Firefox – An up and coming ad and script blocker for both Chrome and Firefox, it also claims to be very CPU and memory efficient. A lot but not too many scripts are blocked out of the box and it’s easy to use with a number of other blocklists readily available. You can also allow or block specific sites from loading on the page via advanced mode.

Ad Blockers not tested

AdBlock Edge (Firefox) – The project has now been discontinued and the author recommends µBlock Origin instead.

AdvertBan (Firefox) – Hasn’t been updated since 2012 and inevitably leaves most or all ads untouched.

AdBlock Lite (Chrome and Firefox) – Left a number of ads untouched on our test sites, even in the more aggressive Full mode. Various sources say the project has all but been abandoned.

AdBlock Super (Chrome) – After reading reviews and doing some testing we found that this addon actually injects ads of its own from a number of third parties. At best it’s adware, at worst it’s malware and should be avoided at all costs. Below are highlighted ads we received when visiting Amazon.com.

µBlock (Chrome and Firefox) – This version is essentially a clone of the original µBlock which was later renamed µBlock Origin. The author of µBlock Origin, Raymond Hill, has since disassociated himself from the µBlock branch and no longer contributes to the project. For these reasons we will test only µBlock Origin.

How We Tested the Ad Blockers

Testing websites can be tricky because ads are served by third parties so a page is depending on external servers during loading. To try and even out any inconsistencies and also any differences with other servers being used by the website, each webpage tested was refreshed 10 times in succession and any times considered abnormal were discarded and the page refreshed again. Then we looked at 3 different scores:

Google Chrome:

Page load time – An average taken for the page to load 10 times. We are using the Load event to time when the browser has finished retrieving all the resources required by the page. In Chrome this is a red score on the Network tab in Developer Tools. Caching is disabled so resources are refreshed each time.

Peak memory usage – We watched the memory usage of the ad blocker’s process in the Chrome Task Manager (Shift+Esc), the maximum amount of Megabytes used during the 10 page loads was recorded.

Peak CPU usage – Similar to memory usage, using the Chrome Task Manager the maximum percentage of CPU usage was recorded during the 10 page loads.

Mozilla Firefox:

Page load time – Average time taken for the page to load 10 times. Firefox doesn’t have a separate load event time in its Network tab like Chrome does, so we used an addon called app.telemetry Page Speed Monitor to get the times.

The frustrating thing about Firefox is you cannot get accurate scores for memory or CPU usage of extensions during use because unlike Chrome, everything is loaded into a single process. The about:memory page and a few related add ons don’t give a true live score for memory usage. As a result we could only record results for page load times in Firefox.

Tests were conducted on a 4GB, Core Duo 2.2Ghz laptop using WiFi and running Windows 7 as the operating system. Although the tests could have been run on a more powerful system, we believe the laptop will produce more representative scores for the average computer.

All ad blockers were installed and used with their default settings, nothing else was changed. The only exception is Ghostery which runs a wizard on startup where you need to choose what to block, for that we selected only the Advertising blocking option. Chrome 44 and Firefox 40 were the browsers used for testing.

Next we’ll test 10 websites to see how the ad blockers perform.

Tested Websites and Results

We chose 10 websites to run the tests on, they have a mixture of themes that an average or tech minded user might visit. In general we’ve picked sites that are not too fast to load all content or have a sizable load time difference between showing ads and blocking ads.

CNN.com

Many articles and reports have highlighted news sites as one of the worst types for advertisements, so a major provider like this should be a good starting point. CNN.com doesn’t seem too bad, we noticed 4 ads on the home page and promoted stories from outbrain inside the articles. This is a content rich site and that could affect the time differences between ads and no ads.

AdBlock Plus is noticeably slower while µBlock Origin and Ghostery are both a small amount quicker than the rest. Ghostery was also best in memory usage while AdBlock Plus was by far the biggest CPU hog.

The Firefox CNN load times were quite similar although µBlock Origin managed a small advantage over µ AdBlock, which had a small lead over the others.

PCAdvisor.co.uk

PC Advisor is the UK branch of the American online PCWorld magazine. We originally intended to test pcworld.com but when it was found that pcadvisor.co.uk has far more and far bigger ads which can take up an astonishing 3/4 of the browser window, we switched to PC Advisor.

There was a reasonable time difference between the fastest (µBlock Origin) and the slowest (AdBlock Plus) in Chrome. AdBlock had CPU and memory spikes midway through the test, interestingly all the other AdBlock based addons suffered with the same problem.

Firefox didn’t like this page and often displayed 2 header ads on top of each other and was often very sluggish when loading. Things improved with an ad blocker where µBlock Origin was noticeably faster.

Airliners.net

The Airliners name popped up a few times on the internet as somewhere with a more than reasonable amount of ads. Unsurprisingly Airliners is an aviation website with information and news about aircraft. A pop in ad periodically appears on the homepage, the search pages however, have five ads and taboola sponsored links so we tested one of those.

Ghostery’s load time in Chrome was the slowest and it had issues with some on page Javascript. AdBlock Plus was second slowest with µBlock Origin the fastest by half a second. µBlock Origin and Ghostery were the best on memory usage.

µBlock Origin was fastest in Firefox too, and by quite a distance. Ghostery also suffered the same problem as it did in Chrome and got stuck on one of the pieces of Javascript.

CNET.com

CNET is one of the biggest technology news and review sites around and the download.com subdomain is a huge portal for software downloads. CNET is one of those guilty for starting off the trend of bundling adware wrappers with their software downloads. The homepage is content rich and displays 4 ads so it’s debatable how much difference an ad blocker will make.

Most Chrome ad blockers were able to cut load time by more than half, with µBlock Origin eeking out a tiny lead over Adguard. AdBlock and SuperBlock were both higher on memory and processor usage.

µBlock Origin was fastest in Firefox, over a second faster than AdBlock Plus and nearly a second over Ghostery.

Tmz.com

What makes Tmz amazing is not its entertainment news, but the sheer size and amount of content that needs to be loaded. The homepage alone requires over 600 requests, 10MB+ of data transfer and over 50 third party scripts, all of which cause high CPU usage and a slow time to completely load the page.

Ad blocking shaved a massive 20 seconds off load time and µBlock Origin was the only one under 10 seconds. Three blockers exceeded 100MB for memory usage while several suffered high CPU usage due to the page size, Simply Block Ads! especially.

Firefox didn’t like this page at all and we couldn’t get consistent readings to run tests, on every refresh the browser would simply not respond or crash. For this reason we’ve excluded Firefox from testing TMZ.

Moviemistakes.com

On first look Movie Mistakes doesn’t look that bad with 5 or 6 ads on the page and no bandwidth hogging large images or animations. The page loading slows because there’s more than 25 ad scripts downloading from various third parties, each of which takes time and slows overall progress down.

Almost all the Chrome ad blockers reduced load time by over 75%. Adblock Plus was the slowest by a second while none really suffered too much for memory memory and CPU cycles. Ghostery was incredibly efficient being the fastest and the second lightest on memory.

For Firefox the difference was similar with Ghostery being noticeably faster than the other blockers tested.

Sourceforge.net

Sourceforge hosts a lot of open source software and hit the headlines a few years back by including adware in some of the software which caused developers like GIMP to leave in protest. While there are five ad banners on the main homepage, it does load consistently fast so you are not heavily penalized for allowing the ads.

The best ad blockers in Chrome can reduce load time to a lightning fast 1.5 seconds. Most of the memory and CPU usage scores are quite low. One anomaly is Adblock Plus which uses more CPU and loads the page at almost the same speed as the page with ads.

The Adblock Plus result is similar in Firefox with a notably slower load speed, the rest are spread by only 0.3 seconds.

Tomshardware.com

Tom’s Hardware is one of the biggest hardware and software news and review sites. The time to completely load the homepage was consistently over 20 seconds and it has 3 or 4 large ads near the top, and an ad from time to time that covers the entire window. The number of ad and tracking scripts is over 50 which affects the page load time.

In Chrome all the scores were pretty even although µBlock Origin had an advantage in load time and CPU usage, Adguard and Ghostery again stayed consistent. Adblock and its forked versions were all higher for memory usage and CPU load was generally high with three blockers hitting 20%+.

For Firefox it was a similar story with the slowest (Ghostery) less than a second behind the fastest (µBlock Origin). It’s worth noting that Adblock Plus displayed an “acceptable ad” on this page.

Megagames.com

Megagames has a bit of everything for gamers, including news, reviews, cheats, trainers and even game fixes (no-cd patches). This website doesn’t begin to load for 2-3 seconds, and a ton of ad, tracking and analytic scripts extend the overall load time by a sizable amount.

The best and worst times are only split by 0.5s and so close to be unnoticeable in real life. Ghostery, Adguard and µBlock Origin are again good on memory and processor usage while there were no terrible scores to write home about.

Times are also close in Firefox with Ghostery just slowest by a single tenth and AdBlock Plus fastest by a single tenth. The savings by using an ad blocker for Megagames are smaller compared to some other sites due to the overall slower page load time.

Raymond.cc

While we’re testing other sites, it’s only fair we should test our own, because like almost everyone else, Raymond.cc uses ads to help pay the bills. There’s a maximum of 3 ads on any page and none on the homepage or index pages. To test a page with ads, we have used one of our most popular articles as the test page.

The normal page loading in Chrome was just over 3 seconds, an ad blocker cut this time in half and by two thirds for Ghostery and µBlock Origin. The memory usage was quite low across the board and only AdBlock Pro caused slightly higher than average CPU usage, at 12%.

Like Chrome, the Firefox times were tightly bunched and close enough to be unnoticeable in general use, µ Adblock was just fastest.

We’re quite pleased that during the tests our pages with ads displayed were comparable in load time to many sites where the ads are blocked, and the time difference between blocked and viewable ads is usually only around 2 seconds. This means you are not heavily penalized if you wish to continue to show the ads or enable the viewing of ads in your ad blocker.

We’ll now look at the combined scores and pick out the overall winners and losers.

Overall Results and Summary

It’s time to look at all the scores from the test websites as a combined total to see what the ad blockers have done overall.

Combined Chrome Results

Here are the combined average scores for all 10 websites in Chrome.

Page Load Time:

The results show that on average an ad blocker can reduce the time it takes to load a page with ads by around two thirds. Most averaged 3.6 – 3.8 seconds with a time to display the untouched page of 10.5 seconds. Two stand out, AdBlock Plus for being noticeably slower than the rest, and µBlock Origin for being a good 0.4 seconds faster than anything else. Ghostery would’ve been faster if it hadn’t tripped up at Airliners.net.

Average Peak Memory:

There’s certainly more of a difference in the average peak memory usage, Ghostery was incredibly efficient averaging a peak of 37MB across all 10 websites. Adguard was also very consistent and rarely strayed far from its 52MB average. The previous winner µBlock Origin is second but it’s memory usage did vary a bit site by site. SuperBlock Pro was the highest memory user, followed by AdBlock and AdRemover.

Average Peak CPU:

µBlock Origin won this time as well, being the least taxing on the CPU by an average of almost 2% over Ghostery, Adguard was a close third. AdBlock and the AdBlock based extensions all struggled to control their CPU usage on a number of sites. AdBlock Plus was the most CPU intensive, more on that below.

Combined Firefox Results

Here are the combined load times for all 9 websites in Firefox (tmz.com wasn’t tested).

Page Load Time:

Although not what we’re looking at, it’s interesting to see that Firefox was slower than Chrome to load our test pages in all but one test. All Firefox ad blockers were very close in the end, but like in Chrome, µBlock Origin managed to get a 0.4 second lead over everything else.

AdBlock Plus Anomalies

If you’re wondering why the popular AdBlock Plus got low scores in some Chrome tests, the answer is simple and it’s purely down to the acceptable ads check box. Disable “Allow some non-intrusive advertising” and AdBlock Plus will performance wise, sit in the middle of the pack.

Whatever your opinion on acceptable ads, using the option in ABP is not recommended and if you wish to support showing specific ads while browsing, use something else. AdBlock, Adguard, AdRemover and SuperBlock all have an acceptable ads option of some sort, but none suffer a performance drop like ABP.

Multiple Tabs

What might surprise some is that with 10 tabs open and all test websites loading at once, an ad blocker’s memory usage doesn’t alter massively, the CPU usage can go up but it’s not a cumulative increase and having 10 tabs open won’t increase memory or CPU usage by 10 times. What does go up is the strain on the browser itself while loading multiple tabs, and it will use far more memory and processing power.

A more efficient ad blocker is preferable in this case so it and the browser are not fighting over resources. On the whole, an ad blocker’s memory usage is not a major concern with multiple tabs open, but its CPU usage can be, and the less CPU cycles taken from the browser itself, the better.

Overall Winners

The overall winner in Firefox is simply the quickest, and that was µBlock origin. µ AdBlock is a fair choice if you want an easy to use but fast blocker, the rest are almost identical so it’s down to personal preference and the options available as to which one you use.

The winner in Chrome is a closer call when you consider the results from all three tests. But as it got a couple of firsts and a second, we would say µBlock Origin is the definite winner, it truly is fast and efficient as the author claims. Both Ghostery and Adguard are still excellent choices and are viable alternatives to µBlock Origin providing good performance in all 3 categories.

If you disable acceptable ads, Adblock Plus goes from being dead last to a blocker that performs similar to the rest. It’s worth pointing out AdBlock and it’s forked versions all suffer with higher CPU and memory usage, for that reason we would recommend something else if you have a low end system.

Of course, every web site, computer and internet connection is different and you would likely get slightly different scores on your system. But when the ad blockers are tested altogether in a controlled environment, the trends should be similar with what we have here. Also changing settings and adding/removing block lists will also likely have an effect on all 3 scores, which is why we left all ad blockers at their default settings.

Don’t forget, this test has been about the performance impact an ad blocker has on the loading of a page and the system’s resources consumed in doing so, it does not take into account other factors such as how many features are available and what can be blocked in additions to advertisements.

Final Note

Whether you think they are good or bad, ad blockers are here to stay for the foreseeable future and it’s up to each individual website to strike a balance between providing the well placed ads they require while not annoying people so much that they feel there is no choice but to use an ad blocker. If you keep your website loading fast and efficiently both with and without ads, it increases the likelihood people will not block the ads on your site or they will be more willing to whitelist your site in their ad blocker.