SD cards are a great way to expand the storage in your phone, but they're not always the best solution if you want to use them to run apps.
Now, a new labelling system for SD cards, part of the Secure Digital 5.1 spec released by the SD Association (SDA), will tell you how well the card can run apps.
The first class is called A1, with more classes to follow, and denotes sustained sequential performance of 10 MB a second along with 1500 random read IOPS (input/output operations per second) and 500 random write IOPS.
Basically, that means if you see the A1 symbol on an SD card, and on the device you're using it with, you will have no problem running apps off the card.
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The SD Association says the new SD Specification 5.1 establishes the new "Application Performance Class" allowing users to both run and store applications on SD memory cards, as well as store all the usual files.
Brian Kumagai, SDA President, said: "With its consumer-friendly symbol, App Performance Class eliminates buyers' frustration with identifying app-running compatibility on their Android devices and microSD memory cards.
"Matching the App Performance Class symbol with your mobile device requirements simplifies the process and continues the SD tradition of matching your memory card to your device."
Google's introduction of "Adoptable Storage Devices" on Android Marshmallow last year further popularised the idea of using SD cards to run apps.
However, not all SD cards could be used as adoptable storage, as most are optimised for storage of files rather than for running apps.
The SDA has designed the App Performance Class symbol to allow manufacturers to communicate that their SD cards come with all the necessary app-running requirements.
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Let us know what you think of the new SD card spec in the comments.