How we test mobile phones

At Which?, we go further than anyone else to find you the best smartphone – our independent test lab conducts more than 300 individual checks, including using a robot arm capable of thousands of interactions to test battery life.

We also purchase every phone we test, not from the manufacturer, but from the retailer – just as you would. This means we're not beholden to the likes of Apple, Samsung or Xiaomi, and you can be confident there's no bias in our scores.

It also means the phone we're testing is exactly the same as the one you'll hold in your hand, without any special features like extra RAM to try and improve performance.

Most free mobile phone reviewers are subjective and produce a score that reflects their preferences. Ours are objective – they rely on data to find you a Best Buy. And if a phone can't hack it we label it with a Don't Buy warning.

We lab test more than 65 smartphones a year, find the best mobile phone reviews to compare every model we've tested.

Mobile phone camera quality: Can the phone capture the perfect shot?

Camera quality can vary hugely depending on the environment the phone is in, which makes this test particularly technical. That’s why we test every handset in 10 different shooting environments and measure them against a variety of criteria. 

We use mannequins of different skin shades to see how well the camera picks up all skin tones, and shoot different objects to see how well the camera picks up texture and detail.

We look at how well phones do the basics, such as deliver good overall picture quality, all the way up to more advanced features such as producing good flash uniformity and colour accuracy. We also take into account how the different lenses perform, as well as the speed of the shutter, and quality of the zoom and auto focus features.

Taking photos is only one part of how well a camera performs. We also look at how well a phone captures videos, and how well the image stabiliser works, so you know whether your phone will capture clips with the same high quality as its videos.

What separates a good result from a poor one?

To earn a 5-star rating, a camera must have outstanding overall picture quality with sharp details and true-to-life colour accuracy, including fair skin tone rendering. Those scoring 3 stars might struggle to provide decent flash illumination, precise autofocus, or robust optical zoom. Avoid those scoring just one star as they're unlikely to do well in low-light, or the video performance could be glitchy and unsmooth.

Jamie Darlow, Which? smartphones expert, says: 

'You've told us that camera quality is vital on any smartphone, but you don’t have to spend a fortune to get something that will take brilliant photos. Yes, flagship models from the big brands have incredible hardware, but our tests show you can take great photos without spending a fortune. Check our mobile phone reviews for more. 

Mobile phone battery performance: How long does the phone’s battery last?

We use a robotic arm to test the battery life of each phone we test, cycling through a range of apps and features to give you a realistic idea how many hours it'll run before the screen goes blank.

One of the most important tests of any phone is how well its battery lasts after it’s been fully charged. It’s customary for manufacturers to make tall claims about how well a phone’s battery performs and our tests uncover whether they're true or not.

The robotic arm is designed to mimic how you use your phone, watching videos, making phone calls, using the camera and navigating through a map app. We measure how long the battery lasts to see how well the phone can keep up with your typical day.

We also check how long each phone takes to reach full charge as well as the battery percentage after 15 minutes of charging, so you know whether the phone charges quickly in a pinch.

What separates a good result from a poor one?

Most modern phones now have reasonable battery life, and even the least long-lived models can run for as long as you're awake without needing a charge, according to our testing. If you’re a heavy social media user or you watch a lot of videos, though, you’ll need a lot more juice – many phones rated five stars for battery life could last twice as long, and quick-charge to over 30% in just 15 minutes.

Mobile display: how bright and clear is the display?

Other reviews quote manufacturers’ claims when assessing brightness, usually in units called nits, but at Which?, we measure the light coming from our test model’s screen and tell you what that means in the real world.

We put every phone through multiple scenarios to evaluate the quality of its display, by assessing it in standard and demanding lighting conditions, using microscopes to assess sharpness and resolution.

Each phone is confronted with challenging situations, including low-light environments with high reflection to simulate what you’d experience on a train or any other area with frequently changing lighting. 

We also check how quickly a touchscreen responds to make sure it can keep up with all your texting and browsing.

What separates a good result from a poor one?

A phone with five-star screen performance needs to really pop in a range of lighting conditions. It will be bright even in strong sunshine, with vivid colours and sharp edges. Avoid phones awarded three stars or less because they’ll have fuzzy screens and won’t get bright enough, particularly if you’re looking at the screen off-centre.

Mobile phone performance: Will the phone struggle with intensive tasks?

We test the speed of the processor, and record how responsive the phone is during various tasks.

No one wants their phone to spend ages loading just to show an internet webpage. It’s important for your phone to be able to keep up to speed when you’re using it, so we test each handset to see how quick its processor is. We benchmark the speed of each phone’s processor and also put them through a series of day-to-day tasks to see how well they hold up.

What separates a good result from a poor one?

The best phones for speed have the ultimate combination of a fast processor, ample ram, and a zingingly-fast refresh rate on the touchscreen. This makes them capable of multitasking without missing a beat. Phones scoring two stars or less grind to a halt when you ask them to perform anything more than everyday tasks.

Mobile phone call quality: Do calls sound loud and clear?

We test how good the quality of phone calls are on a mobile phone, making calls to and from the phone to evaluate how well it copes in different environments.

Like many of our other tests, we don’t just test the phones in one environment. We test them in a normal, quiet lab setting, and check how well it would deal with disruptive background noise. We listen to see whether you and the person on the other end of the line can be understood clearly, how well the noise cancelling works and if there is a good level of volume.

What separates a good result from a poor one?

Phones with three or four stars for call clarity might be too quiet for some users, or fail to cancel out background noise. The best performers have rich sound that’s crystal clear, without any interference.

Mobile phone durability: Is the phone built to last?

We go above and beyond to test phone durability – the latest folding phones' hinges are tested 50,000 times before we pass judgement.

Our expert lab technicians assessments go beneath the surface, to make sure you’re buying a phone that lasts. Testing the durability of the mobile phones includes the quality of its display and to make sure it can also withstand conditions such as heavy scratching from a key if it’s chucked in your bag. 

We also check how well a phone would survive being rained on. And if the manufacturer claims it's waterproof, we submerge it in water, just to make sure.

What separates a good result from a poor one?

After 100 drop tests, scratch testing across lenses and screens, immersion in water, and a host of other checks, only the best phones emerge unscathed with five stars. Poor performing phones develop deep scratches, faulty microphones and speakers and, occasionally, broken screens.

Mobile phone ease of use: Is the phone easy to handle and navigate?

Our lab technicians use their years of experience to scrutinise various features of how a phone is used from general usage to how sensitive the screen is.

Important factors such as how good a phone’s security features are also come into the ease-of-use rating, but we still take the fine details of a phone's functionality into account, such as how easy it is to view large amounts of texts on the default internet browser. This means you won’t be stuck with an expensive phone that’s a pain to use. 

What separates a good result from a poor one?

To score five stars a phone needs to be intuitive to use, with a menu that flows seemlessly from one app or function to the next and a touchscreen that reacts instantly to your finger or the phone's stylus. It should also be easy to unlock the phone, get the camera, and perform a host of other functions. At the other end of the spectrum, we've tested phones that allow intrusive pop-up ads, are hard to set up and unlock, and are lumbered with slow internal storage

Mobile phone security: Does the phone keep your data safe?

Uniquely, we calculate how much time is left for each phone before it stops receiving security updates. There’s no point buying an otherwise-brilliant phone if it’s unsupported and vulnerable to hackers.

Your phone knows more about you than most, so you want to be confident that it keeps this information safe. We put each phone through our security tests to see how well it guards your data.

We check phones regularly for security updates – crucial software that keeps your phone secure. If manufacturers stop updating older phones, we remove any Best Buys and Great Value labels.

If a phone has face recognition software that can be fooled with a 2D photograph, we check to see if there is a clear and specific warning in place to tell you about this insecurity. 

What separates a good result from a poor one?

Phones that can be fooled with a 2D photo and that don't have an adequate warning don't qualify for Best Buys, despite how well they might otherwise score. We also look at whether there are regular software updates and how robust the password protocol is.

Which? members can filter all our mobile phone reviews by battery life, camera performance, display quality and more, with our expert test results 

How we calculate the scores

Jacob Compton, Which? scientific advisor, says:

'We regularly ask Which? members what matters most when choosing a new phone. I then use this information when developing the test program and evaluating the data from the laboratory. Since members said the camera, battery life and the display matter most, they carry more weighting than other elements of the testing when calculating the score.'

Here are the weightings for each element of the test:

• Camera - 20%
• Battery - 15% 
• Display - 15%
• Performance - 10%
• Sound quality - 10%
• Durability - 10%
• Ease of use - 10%
• Phone functionalities: 5%
• Capabilities - 3%
• Security - 2%

How we choose the products

We go to great lengths to ensure our reviews are 100% independent and unbiased, and it begins with how we source mobile phones. We never accept freebies from manufacturers and brands, which means our scores can’t be influenced by anything other than our lab results.

Instead, we invest over £65,000 a year buying and then testing phones. We review at least 65 smartphones annually, and bring you hands-on first look reviews to give you our personal experience of using a phone. That means we can be both thorough and speedy when it comes to the latest releases.

It’s not just the latest flagship phones that get our attention, we’re also interested in the more budget-friendly phones that slip under the radar. Often, they use the same processors and screens, but can cost hundreds less.  

Sarah Hiscock, Which? market analyst, says:

‘I choose products from the usual suspects, such as Apple, Samsung, Xiaomi and more to find the key models you’ll find at major retailers like John Lewis, Currys and Amazon. But I also cast the net wider for the best market coverage, and include Nothing, Honor, Oppo and more. It’s not just the latest flagship phones that get our attention, either. I also actively choose budget-friendly phones, which sometimes use the same processors and screens, but can cost hundreds less.’

While we also occasionally do hands-on first look reviews to give you our personal experience of using a phone, the Which? overall score is generated solely from ratings and results that we receive from our independent lab where these phones are tested under identical conditions, so they're directly comparable.

Is it a Best Buy mobile phone? What our verdicts mean

The stakes are high for mobile phones, so we only give our Best Buy recommendation to the very best models on the market. A mobile phone that scores more than 77% based on its performance in our lab is made a Best Buy. That said, Best Buy phones aren’t perfect, so it’s still important to read our review to find out what weaknesses each phone has. Not all our Best Buys are expensive, but consider a Great Value phone if you’re looking to spend less on your next smartphone. On the other end of the spectrum, a mobile phone that scores 45% or lower is a Don’t Buy. 

• Best Buy mobile phones typically earn their score by delivering in the most important areas – an enduring battery that also lasts well on a short charge, excellent camera quality, and features and functionality that make it easy to use.
• Great Value mobile phones might not have the most premium displays or cameras, but you get a lot for your money. Our Great Value handsets score 60% or more in our tests and they're at least 20% cheaper than the average price for all mobile phones we review.
• Don’t Buy mobile phones struggle to do the core tasks well – the battery may not last long enough, pictures could be poor quality, it could be difficult to use or a combination of all three.

We don’t award Best Buys or Great Value to mobile phones now only available second-hand because the performance of a second hand or refurbished phone might differ from buying a new one that we test in our reviews. We also don’t award Best Buys or Great Value recommendations to mobile phones with less than two year of security support left. Read our guide on mobile phone security for more. 

How is the Which? score calculated?

The Which? overall score is a percentage. This score only takes into account the results of our tests and ignores price. As of 2024, we changed our testing protocols slightly to keep up with new developments in technology, so these are not 100% comparable with older reviews. However, most of the test have remained the same so you can get an idea of how any mobile phone at any price measures up against its rivals.

Weightings and star ratings

A Which? overall score is made up by testing various criteria, from key ratings such as battery life, camera performance, ease of use, audio quality and durability. Behind each of those ratings includes more than 40 individual tests and checks that are weighted differently. This means that the most important things, such as the quality of your pictures and videos, will more greatly impact the score than features such as how easy it is to use the phone’s music player. 

To keep things simple, the most important scores are shown as star ratings out of five on each phone’s Test Results page, as an easy-to-compare list of strengths and weaknesses, so you can quickly work out whether a model is right for you.

Our smartphone experts

We run our test projects collaboratively, with dozens of experienced researchers, scientists and market researchers contributing to each area. This means we can re-evaluate the test program each year to ensure it’s of maximum benefit, using the Which? community to focuss on the phones that matter and the functions that mean the most to you.

Here's the core smart phones team members that makes it happen:

• Senior researcher & writer, Jamie Darlow: Jamie’s been hands on testing tech for nearly two decades, but he’s also a dab hand at translating technical lab reports into in-depth, unbiased product reviews. He can see marketing fluff and technical jargon a mile off, and cuts through it to break down each phone’s pros and cons and separate the truly smart phones from the phoneys.
• Tech editor, Paul Lester: Paul’s been immersed in tech his entire life, and considers it his personal mission to translate that passion to you. His job is to make sure what you’re reading is exactly what you need to know about the latest phones - that means keeping an eye on the latest releases, finding the consumer questions you need answering, and picking through data to help empower our readers.
• Scientific adviser, Jacob Compton: Jacob helps develop the test program, instructing the lab on its testing processes and converting the hundreds of points of data it gathers into scores and star ratings. This rigorous scientific approach means only the best phones are awarded Best Buy badges.
• Market analyst, Sarah Hiscock: Sarah constantly monitors the mobile phone market to shape our review schedule, making sure our content focuses on what matters most to you. Whether it is a flagship from a well-known brand or a device from an up-and-coming company, we cut through the advertising noise to test the products you are considering for your next upgrade.

Now, check out our mobile phone reviews to find the phone that suits you.