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How we test external hard drives

By Jon Barrow

We subject all the hard drives to the same tough lab tests so we can clearly recommend which models to buy – and which to avoid.

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How we test external hard drives in a nutshell

We test every external hard drive in the Which? test lab to the same high standard and ensure that each of our reviews answers your key questions. These include:

  • Is it easy to set up and connect to my computer?
  • Can I speedily copy files to the drive and quickly access content that I've already saved?
  • Is the drive well built?
  • Does it have built in software that I can use to protect my data?

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All the drives are assessed in a test laboratory using a Windows 10 computer. We set up and install each of the drives as a typical person would and then load a variety of files, all of different sizes, on to three separate parts of the drive.

We then measure the transfer rates when saving the files and also when trying to retrieve them.

The best drives offer blisteringly fast speeds while the worst chug along slowly and can seem to take an eternity to copy very large files such as full length HD movies.

But it's not just the speed of data transfer that can make the difference between a good and bad drive, niggly things like too short leads or poorly positioned buttons can end up becoming a real irritation.

Drives also get marked down if they are noisy, get too hot or if they guzzle power – especially when they are just idling.

Best hard drive brands - discover which brands impressed when we asked almost 2,000 Which? members to rate their hard drives.

Capacity and software

We rate each drive for the storage capacity it offers. And we don't just take the manufacturer's word for it – we check the actual usable storage that you can access.

We also give extra marks if the drive offers valuable features such as built-in encryption software to better protect your files or access to online cloud storage options.  

Should I buy it?

Each of the assessments described above goes part way to making up a total test score, which is the percentage figure awarded to each external hard drive.

But certain assessments are more important than others and so carry different weights (price is always ignored):

  • Performance/speed: 60%
  • Ease of use/portability: 15%
  • Capacity/connectivity: 10%
  • Build quality/noise: 10%
  • Power usage/temperature: 5%
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