Skip to main content

SD 5.1 spec will help you identify if your card can handle apps with new 'A1' badge

The SD Assisciation (SDA), which handles the specification for SD cards of all types, has unveiled its latest spec, SD 5.1, including a new distinction for SD cards that are designed for application use rather than just media storage. The new specification, called "A1" (or App Performance Class 1), shows that a given SD card meets certain performance standards set by the SDA that determine it's good enough to be used as a storage device for apps.

The new SD 5.1 spec comes as a (much delayed) response to Android 6.0 Marshmallow's introduction of Adoptable Storage in which an Android device can fully adopt an SD card as part of the internal storage rather than simple removable media. As many people have found, using a cheap or slow SD card in a device that's using Adoptable Storage can be detrimental to the experience of the whole phone.

In order for an SD card to be considered A1 compliant, it has to provide random read IOPS (input-output access per second) of 1500, write IOPS of 500 and sustained sequential performance of 10MB/s. Though many high-end cards will already meet these standards, some on the bubble that purport to have greater speeds may not actually offer them in a sustained manor or be able to offer high enough IOPS performance for regular app use.

Adding another level to this is a certification process for phones and tablets themselves to be considered A1 compliant. The SDA will offer manufacturers the opportunity to test their phone or tablet's own hardware to make sure it can accept these speeds for an optimal Adoptable Storage experience, though the cards themselves are far more often the weak point in this equation.

The A1 badge, which you can see above, will soon be found on packaging for SD cards and potentially phones and tablets that have passed the certification process from the SDA. As higher speed needs emerge, the SDA has said it plans to introduce higher levels of compatibility, i.e. A2, A3 and so on.

Andrew was an Executive Editor, U.S. at Android Central between 2012 and 2020.

  • What does it matter Google seems to prefer to phase them out. Why even make adoptable storage and none of your own devices support it?
  • Google hasn't included a Micro-SD card in their Nexus/Pixel phones since 2010. If Google was trying to phase them out through their own actions, no manufacturers would be using Micro-SD cards. In announcing adoptable storage, Google specifically said it was for low end, low storage devices like Android One or a $100 phone from a generic manufacturer. Not for a flagship-speed device. Also, the Nexus Player includes a USB port, which can be used with Adoptable Storage, so one of their devices DOES support it.
  • I'm glad this is near the top. When this discussion comes up people bang on about Nexus or GS7 or whatever high end phone that doesn't support it. People don't think outside there own circumstances and adoptable storage is a great way for Google to make low cost devices able to download plenty of content from the play store.
  • The GS7 does have a micro SD slot. Samsung removed it from the S6 line and put it back after complaints. Nowadays iPhone aside, only Google and hTC nolonger support it. Most other manufactures still do thankfully.
  • Yes the S7 accepts SD cards, but it does not support Adoptable Storage, which is what they are taking about here. Also, most if not all recent HTC phones have SD card slots.
  • Just because something is in Android doesn't mean Google's own phones have to support it. I would think that people would appreciate that Google continues to create features even if they're not precisely what it want to do with its own phones.
  • FINALLY! I think this is the first time ever they've used random I/O for any sort of official spec/certification, instead of sequential transfers. They should've done this at least half a decade ago, not merely as a response to adaptive storage. It would've helped Widows Phone and loads of other phone and non-phone usage cases where people had no clue what they're getting without finding a review.
  • SD is a dying standard anyway. I really don't see how they can even compete with UFS cards at the same size with SATA SSD speeds. I mean you can put a new A1 badge on a 7 year old micro SD card, but it's still a slow, old card.