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Updated: 25 May 2022

How we test wi-fi routers and extenders

Discover how we assess wireless routers and extenders in our test lab. Only the cream of the crop earn our prestigious Best Buy award.
Hollie Hennessy
Best buys

Which? tests wireless wi-fi routers and extenders so that you know which one will give you the best wi-fi signal in your home. We put all the big-brand wi-fi routers and extenders through their paces so that we can help you choose one that's quick to transfer data, easy to use and offers decent signal strength.

Each wi-fi router and extender is subjected to the same set of gruelling tests so that we can compare them blow for blow. This means that we can answer your important, no-nonsense questions with confidence and give you a verdict you can trust. We’ll answer key questions about:

Head straight to our wi-fi router and extender reviews – or read on to find out more about how we test to answer each of these questions.

How good is wi-fi coverage and speed?

To find out how well the router performs in terms of wi-fi coverage and speed, we use a variety of different tests. Firstly, we test how well the router or extender copes with different multimedia devices, including streaming 4K Netflix, YouTube, audio and online file transfer, running simultaneously around the home. This gives us our first indication of the coverage you'll get, and whether it will be possible to do a few things at once, under a relatively light load. 

But we don't stop there – coverage is also assessed by measuring exact speeds all around the test house. This shows whether the router or extender will give you decent speeds, even at hard-to-reach corners of the home. 

Finally, we test how well the router or booster will cope when there are lots of different devices connected, all requiring a lot of bandwidth. To do this, we transfer data on four different devices, all around the home, and record the file transfer speeds. This tells us how well the router is suited to homes with a lot of people, and whether it will conk out if you're trying to put it under a lot of stress – such as simultaneously downloading things online, streaming different Netflix shows around the house and gaming online, for example.

The below is a heat map that we get from our coverage testing. The greener the colour, the faster the signal is. 

Is the router or booster easy to set up?

Wi-fi routers or boosters can sometimes be tricky to set up, so we assess how easy it is to get each device out of the box and up and running.

We note what instructions come with the router or extender and then assess how easy it is to set up for a beginner and whether it has more technical settings for advanced users.

We also look at how easy it is to set up a local network and apply parental controls.  

Are there any security issues?

Routers might not be the most exciting devices and are often easy to forget about but, as they act as the digital gateway to our homes, it’s vitally important that security is up to scratch. 

We put routers through a full security test programme, to make sure you can be confident that your data is protected.

Data encryption

During set-up and daily use, data is passed back and forth to your router. Encryption of your data means that it’s safeguarded against prying eyes. 

We check that the most important data, such as your personal details, is encrypted, and where it’s going, particularly if that’s outside of the EU. If we spot anything out of the ordinary, we’ll raise an alert and investigate the issue. 


The firmware that your router, booster or extender is operating on can be extremely important. Out-of-date or poorly maintained firmware can mean there are gaps that could allow a hacker to access your device. Checking for any vulnerabilities ensures devices are well maintained with security in place. 

Data transparency

We look at setting up all wi-fi devices online, and on both Android and Apple devices, in case there are any differences with the apps. We check what app permissions are requested, such as your location, access to the camera etc, and the reasoning behind it, to make sure everything you’re giving away really is necessary. 

Password Policy

Setting a strong password may seem basic, but we leave no stone unturned. We assess whether password policies are strong, to avoid easily guessable passwords which could allow people into your network to potentially access your data.

Sometimes a router or booster might allow basic passwords such as ‘password’ or ‘1234’, or even have the same username and password for every device. Also, some models will have a default password, like ‘admin’, and won’t require this to be changed. This can be an easy way in for hackers. If this is the case, we’ll highlight this in our reviews, alongside our advice on how to set a good password.


What happens when you’re ready to upgrade, get a new wi-fi device or are thinking about selling your old router? Our test looks at how easy it is to reset the product and get rid of all of your data. We make sure to check there are no remnants of the previous user’s data too. 

Man-in-the-middle attacks

A man-in-the-middle attack sounds scary, and it can be when your personal data is at stake. It’s when a hacker acts as an eavesdropper, trying to catch information passing to and from your router, extender or booster. 

We run tests on every model to see if it could be susceptible to this kind of attack. If there’s anything to worry about, we’ll make sure not to recommend the product.

Other types of attacks

New hacking threats are constantly emerging, so we make sure to keep on top of the latest risks and update our test programme as necessary.

Google wifi

Should I buy it?

We give each wi-fi router, wi-fi extender or mesh system a total test score, so you can see which are the best and worst.

In each review we summarise what we thought of the router or booster so that you can quickly get the information you need to decide which device is best for you and your needs.

The score for each router or extender is made up of a combination of the elements in the test. We don't take price into consideration – most routers supplied by your provider will be included for free as part of the broadband package.

The score is broken down as follows:

  • 90% performance
  • 10% ease of use

Although the score is broken down in the same way for wireless routers, wireless extenders and mesh systems, each type of device is evaluated in a slightly different way. This means the scores for each type of device are comparable within that category, but not across the three. 

A wi-fi router and mesh system needs to score 84% or more and an extender needs to score 74% or more in our tests to earn our Best Buy recommendation. Models that score 45% or less are labelled a Don't Buy as a warning to avoid them.