Running out of storage space on a tablet smartphone or can be a pain. If your device supports it, adding a microSD card can help. If you never want to worry about storage woes again, the SanDisk Ultra 128GB UHS-I is the highest-capacity microSD card we’ve seen.
It comes with an SD card adaptor so you can use it in a wide variety of devices. SanDisk claims it can read files at up to 30MB/s, but our tests showed it was capable of higher speeds. Reading large files posed no problem, as the card managed a massive 123.21MB/s in our large file test, and smaller files were read at 42.58MB/s. These are some of the fastest speeds we’ve seen from a microSD card.

Write speeds – arguably more important when you’re using the card to take photos and videos – were less impressive. SanDisk doesn’t provide an official figure for write speeds, but the card managed only 14.01MB/s in our large file test, which is below average. Small files were in line with what we’d expect at 5.06MB/s, but SanDisk’s own Extreme 64GB microSDXC UHS-I card trounced the Ultra card in both respects, writing large files at 55.91MB/s and small files at 9.92MB/s.
Both cards were capable of taking at least 30 full-resolution shots on a Sony NEX-5 camera in burst mode without slowing down. The only difference came when we shot in Raw and JPEG: the Extreme managed nine shots before slowing down, while the Ultra card managed eight. This will be disappointing to anyone hoping to use the Ultra for heavy-duty digital camera work, but it should still be more than enough for most users.
We certainly don’t have any complaint about the amount of space on offer, as SanDisk claims it can store up to 24 hours of HD 1,280×720 video or over 70,000 photos if you have an 8-megapixel sensor.
It’s durable, too. SanDisk claims the card is waterproof, shockproof, temperature-proof, X-ray-proof and magnet-proof. We also like SanDisk’s free Memory Zone app for Android, which lets you manage and move your files between the card and your phone.
It’s a shame write speeds aren’t as good as we’d hoped, but the SanDisk Ultra 128GB card’s real-world performance is more than adequate for smartphones and tablets. Not all microSD card-compatible devices can support 128GB cards, so check the maximum capacity before you buy, but if you never want to worry about running out of space again, the SanDisk Ultra 128GB microSDXC UHS-I card is ideal. Katharine Byrne
Write speeds aren’t fantastic, but this is still a great choice if you’re looking to add storage to your smartphone or tablet.


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