Our guide will give you advice on what to look for when buying portable storage. There's no current review for these products.

Whether you're talking about a smartphone, tablet, laptop or even a desktop computer, your on-board file storage space is always going to be limited. This may not have been a problem for most of us a few years ago, but these days our personal file libraries of movies, music and photos are growing at a ridiculous rate, and are quickly becoming too much for our devices to handle on their own. Enter digital storage devices, particularly those of a portable nature. And the more portable the better.

You can take an almost unlimited amount of data with you wherever you go, simply by picking the right sort of file storage device. The type of storage device that's right for you, though, will depend not only on the kinds of files you want to store or their size, but also on what you're planning to do with them.

What are your options?

Portable storage falls into four main categories:

  • portable hard drives (including solid-state drives, or SSDs),
  • USB flash drives (also known as thumb drives), and
  • memory cards (the most popular being the SD card).
  • wireless portable storage (including SSDs, hard drives and devices that can attach SD cards or thumb drives)

Start by asking yourself some questions to work out the right data drive for your needs. For example:

  • Would you like to store a multimedia project, a full set of movies or your holiday photo collection? You might be better off with a portable hard drive (either direct-connect or wireless) for maximum capacity.
  • Do you want to store a few documents or digital photos for printing at a photo kiosk? Then a USB thumb drive will probably do.
  • Are you looking to store home movies from your new HD video camera? The best choice here may be a super-fast, high-capacity SD card.
  • Can you attach these devices directly to your mobile device or would you prefer to (or need to) use a device that connects wirelessly by creating its own personal Wi-Fi hotspot. 

Here's how the different types of portable storage differ:

Portable hard drives

Our constant accumulation of HD movies, digital photos and music files means it doesn't take long before the hard drive on our laptop or all-in-one desktop computer fills up. And the answer to the problem? Store your mountain of multimedia on a large external desktop drive. This kind of storage device comes in two forms:

  • hard disc drive (HDD): These give you the most bang-for-your-buck, with up to 5TB (terabytes) of storage in a compact unit you can probably fit in your pocket. This is enough to store dozens of movies, plus your whole photo and music collection. They're also ideal for keeping a backup of computer data that you may need to take with you. They commonly use a 2.5-inch magnetic spinning disk drive just like your laptop computer. (If you need a high-capacity backup drive for your computer, take a look at our external desktop hard drive reviews and tests.)
  • solid-state drives (SSDs): These are made from memory chips, so have no moving parts. This makes them lighter and more robust than HDDs. They're also a lot faster and use less power, but are generally much more expensive per-gigabyte than HDDs. 


Connecting an external drive is usually a simple matter of plugging it into the right port on your computer and it's right to go – it doesn't need to be connected to mains power as well. External drives will come pre-formatted for either PC or Mac. A drive coming with the right format will save you the hassle of formatting it, but you can generally change the drive format with utility software before using it if you need.

There are three common drive formats:

  • NTFS (for PCs) – the most common and efficient format for large volumes on Windows and Linux
  • HFS+ (for Macs) – the most common and efficient format for large volumes on macOS/OS X
  • FAT32 – can be used across Windows and OS X platforms, but has file size and volume limitations
  • Ex-FAT – can be used on both platforms without the limitations of FAT32

USB flash drives

USB flash drives (also known as USB keys or thumb drives) are one of the smallest forms of self-contained portable storage. Like memory cards, they use solid-state flash memory chips, but have a built-in USB connector. They have become the modern equivalent of the floppy disk, offering cheap, compact and convenient data storage. They commonly range from 2GB to 256GB capacity, but 512GB models are available. The more expensive versions may offer much faster performance or better security such as built-in hardware encryption to protect your drive from access by unauthorised users.

The weak point of the cheaper USB flash drives has always been reliability. Despite having no moving parts, they can be infuriatingly fickle and sometimes fail for no apparent reason. They're relatively slow too compared to a hard drive, so they're mostly used for temporary data storage and transfer. The more expensive units can offer significantly faster transfer speeds and greater reliability, along with security options such as encryption. 

But no matter whether they're cheap or expensive, simple or full-featured, their compactness can actually work against them on occasion – they're small so they're really easy to lose.

On the plus side, the better versions (look for a "name" brand) are becoming more robust and secure. Some now offer built-in, military-grade, hardware-based encryption to keep your data safe. There's also a whole class of ruggedised devices, meaning that they're designed to be protected against impact, dust and water, but you can expect to pay more for this extra peace of mind.

Memory cards

Memory card ports are standard equipment on digital cameras and video cameras, but they're also common on laptop computers and tablets, and even desktop PCs these days. The most popular memory card option is SD (secure digital), which comes in a couple of variations including miniSD and microSD cards. Sony has its own proprietary card, called the Memory Stick, which has several different types including the Memory Stick PRO, Duo, PRO Duo and PRO-HG. Other formats include variations of compact flash cards (CF), multimedia cards (MMC) and xD-cards.

The class of card is important to consider, and again what you need depends on what you're using it for. SD cards come in HC and XC versions and may have Ultra High Speed versions of each (UHS-I, UHS-II and UHS-III). Digital cameras and video cameras, for example, have a speed rating so you need to match the card speed to the device speed.

Do you want to store hours of high-definition video footage? Then go for a large capacity and high speed. Are you more interested in storing and transporting a collection of digital still photos? Depending on how many we're talking about, you probably wouldn't need such a large-capacity card for something like this, and because of likely smaller file sizes speed wouldn't be much of an issue either.

You can largely ignore the other SD card format called SDIO (Secure Digital Input Output). This is designed for more than just data storage and is sometimes used in computer equipment like GPS receivers, radio and TV tuners, RFID readers and network interfaces, rather than for personal file storage.

Storage capacity for SD cards

The SD Association sets the standards for the various SD card formats. Following is a basic guide.

  • SD, miniSD and microSD have a 2GB maximum storage capacity.
  • SDHC (high capacity), mini and micro versions range from 4GB up to 32GB capacity.
  • SDXC (extended capacity) range from 32GB up to 2TB capacity.

Speed rating for SD cards

  • Speed Class 2 is needed for standard definition (SD) video recording.
  • Speed Class 4, 6, is needed for high-definition (HD) video recording.
  • Speed Class 10 is needed for full HD video recording.
  • UHS (ultra high speed) Class 1 (maximum bus speed 104MB/s).
  • UHS (ultra high speed) Class 2 (maximum bus speed 312MB/s).
  • UHS (ultra high speed) Class 3 (maximum bus speed 624MB/s).

What you need to know about encryption

What happens if you lose your drive? Portability is handy, but it definitely increases the risk of theft or loss. Without the safeguard of encryption, somebody could easily get their hands on all your files.

Encryption is becoming more common on portable drives, but poses its own problems and makes the need for backup even more vital. There are two ways of encoding your files:

  • hardware encryption is the safer method, but the downside is that if your hardware-encrypted drive fails, it's much harder – or impossible! – to retrieve your data. The upside, however, is that hardware encryption is much harder to break than software-based encryption and so it's better at keeping your personal data away from prying eyes.
  • software encryption can provide some peace of mind if your drive's stolen, although it's not as fast as the more convenient hardware encryption, which encrypts all files automatically. You can apply software encryption yourself if you want, using a free program like TrueCrypt (truecrypt.org). Or you might find encryption software provided on the drive. Mac users can use the Disk Utility program that comes with macOS to encrypt almost any drive or folder for that platform.

Wireless portable storage

Wireless portable storage devices are mobile data banks that can give you extra terabytes of space that you can access without a cable in sight. These devices include models with built-in hard disk drives (HDDs), solid state drives (SDDs) or can let you plug in SD memory cards or thumb drives. All connect to your smartphone, tablet or even laptop by creating their own wireless (Wi-Fi) hotspot. They also let you connect to the internet at the same time, via a 'passthrough connection'.

They have a big advantage over direct-connect devices in that they can connect to multiple devices simultaneously. So, if you want to carry around a large movie and/or music collection, to keep the kids happy in the back seat on a long trip, for example, wireless portable storage devices can be a sanity saver.

They're relatively easy to set up. Getting your content onto them is as easy as plugging in a USB drive. Then you connect them wirelessly to your mobile device by turning on their built-in Wi-Fi hotspot and connecting to it just as you would connect to your local Wi-Fi network. Usually they have an app for your device that lets you organise your files (some categorise videos, music and documents for you for ease of browsing). Most will also let you copy files from the storage unit directly to your mobile device and vice-versa. This can make them a good temporary backup/archive unit for your mobile device when it gets too full.

In addition to their own app, they often allow you to open a third-party media player such as VLC, for handling various video and audio file formats.The most popular are AVI, MKV, MP4, MOV, and WMV.

The internet passthrough function is handy if you want to browse files on the device while simultaneously having a connection to another W-Fi network linked to the internet. In our testing we found the ease of setting up internet passthrough, for connection to the web at the same time, varied quite a bit. We also found notable differences in connection reliability.

What to look for

Purpose is paramount. Once you've decided on the type of storage solution that suits your needs though, there are some other features that you should think about:


This is one of the biggest considerations. If you want a portable backup, go for the largest drive available that you can afford, preferably twice the size of the drive you're backing up. Backup software adds versions of new and altered files incrementally to your backup set, making it grow over time. Don't let your drive fill up completely or it won't work efficiently – try to allow for at least 20% of unused space.


The most common port is USB 3.0, which is much faster than USB 2.0 in real-world operations. USB 3.0 connections are backwards-compatible with USB 2.0, meaning you can use USB 3.0 drives in USB 2.0 ports, they'll just work slower.

USB-C is becoming more common as PC and laptop makers start to include it in new models. For external storage the fastest and most future-proof kind of drive will use Thunderbolt 3 (which shares the same plug shape and size as USB-C, but at 40Gbps is up to eight times as fast as the basic USB-C spec). 


The enormous capacity of hard drives makes backup software a necessity. Managing terabytes of files manually is time consuming and impractical. Many external hard drives will include backup software on the drive, which is handy if you don't have any. But you don't have to use it if you already have backup software on your PC, or a third-party program. Before you use the supplied software, check if it's a full version, a trial version or a special (limited) version. If it's a trial version, it may be fully functional but time-limited, or or it may be limited in what it can do. If time-limited, once the trial period has expired you won't be able to access your backed up files unless you pay extra for the full version. Ideally, your backup software should be able to do a disk image full backup, which can restore everything in the event of drive failure, including the operating system and all programs as well as your files.

Some backup software also ties in with online backup services to give you automatic offsite backup for a smaller amount of your most important files, as well as your full local backup. This also may be a time-limited or extra-cost option. Other software provided on a portable hard drive can include formatting or power management utilities.

Note that if you're buying an external hard drive to use with a recent-model Mac, you won't necessarily require extra backup software as macOS (formerly called OS X) comes with the excellent Time Machine backup software. However, this will require the drive to be formatted for macOS, which can be easily done with the built-in Disk Utility software. 


Although these days formatting is really only an issue for portable hard drives rather than other kinds of data storage, remember that many high-capacity external drives will come pre-formatted for either PC or Mac. If you don't want the hassle of reformatting yourself, be sure to pick the drive that suits your operating system.

Some manufacturers market drives specifically for Macs, pre-formatted and ready for Time Machine – most notably Western Digital (WD). Otherwise, any PC-formatted (NTFS or FAT 32) drive can be formatted using OS X's Disk Utility software. If you want the drive to be bootable, set it to HFS+, Journaled, with GUID partition table.

Many Seagate external drives come with a modified version of Paragon's NTFS for Mac, which eliminates the need to reformat the drive. However, the cut-down version only works for mounting Seagate NTFS-formatted drives on a Mac. 


Drive failures aren't common, but they can happen to any drive without warning (thus the need for regular backups). Most drives have two or three years' warranty, but this won't cover lost data, just the hardware itself. Always keep a backup and if you're very security-minded, keep a backup of your backup.