What are the symbols shown on the microSD card? Am I Buying the Right One For My Phone?



We Often question ourselves, how to buy a microSD card for our smartphone?

The consideration often comes from the salesman at the IT stores, and yet you have not fully understand what are the true meanings of symbols and specification that tells you about the microSD card you are about to purchase. Take this opportunity to learn a full brief and easy explanation of microSD card symbols and meanings that tells you its performance and features.

MicroSD cards are not the same, so identify its specification.

The microSD card is known to be found in large-scale especially on various gadgets we have been using daily. It is a very straight-forward microSD card that you rarely give it a second thought, because most other users would just buy it and pop it into your device to increase the storage space easily.  In fact besides just its storage feature, it can provide more to its users when they understand the broadness and benefits of the card better.

It’s the truth and sadly to say that neither all microSD cards are produced equally, the reason is because some of the cards work better at loading applications on Android smartphones, while some other cards work better for gaming consoles, GoPro, Video recording device, photography, and other devices usage.

The extremely small difference in microSD card selections are what alert us to compile a simple purchasing guideline to assist you better purchase the right type of card for your necessary use or gadgets. Other than knowing the core specifications you can find out on your favorite branded cards, we would like to share with you the basic shopping tips as a guideline.

MicroSD card size to consider only?



At first consideration of higher capacity due to lacking storage space on the current devices, that is pretty normal for every buyers. However based on higher card size as the only purchasing reason shouldn’t be the only specification to care more, because the rest of the symbols indicated on your microSD cards truly shows its overall performance.  as first Storage size is one of the first considerations, but it shouldn’t be the only spec to care about because the rest of the symbols on your card indicates its overall spec’s performance.

Symbols found on your microSD card indeed were coming from a standard introduced by an organization called SD Association. Standards were found by huge memory companies of SanDisk, Panasonic and Toshiba on 2000 years of SD Association with attempts to simplify all specifications that influence the performance of microSD cards. You may have heard of these symbols, but never know what those symbols mean on your microSD cards.

You should have seen the symbols on a microSD card, which symbols indicate as follows:

  1. Storage capacity,
  2. UHS (Ultra High Speed) Speed Class,
  3. Speed Class,
  4. Application Performance Class,
  5. Type of Cards,
  6. Video Speed Class.

Capacity Size

The capacity or storage size is shown on the microSD card in gigabytes (GB) unit and commonly found in size of 32GB, 64GB, 128GB, 256GB, 400GB and higher size in future until 2TB. The capability of maximum storage could be available in future for SD and microSD cards for card type SDXC is 2TB, however the highest known microSD capacity now already available at 1TB Extreme microSD card.

SD Card type

You should aware this if the device you are using is from 2009 or earlier years. The available card type starts with the first generation’s named as SD (Secure Digital) card type, which then followed by SDHC (Secure Digital High Capacity)  card type, and the latest generation was named as SDXC (Secure Digital Extended Capacity) card type. These card types were introduced based on a different technological age, thus any old device that supports up to SDHC was unable to use the new SDXC card. As your devices are newer and can read the latest card type (SDXC support max up to 2TB), then they can also accept the older generations card type.

Types of SD Card’s Format

Max Supported Capacity File System Type Backwards Compatible


sandisk 2gb microsd



sandisk 32gb microsd sdhc

32GB FAT32



Sandisk microsd sdxc




Speed Class:

We should know that recording video in fact requires a constant minimum write speed to prevent ‘frame drop’ especially while recording in order to achieve a smooth playback.

This is why the speed class of the card requires it to be at its minimum sequential write speed, which is very important for video recording smoothness. SD Association ongoingly upgrades their marketing strategies for sequential write speeds, which gets complex and difficult to keep up over time. Here are the well-known three advancement called as class of:

  • Speed Class Mark – was indicated with a symbol showing a number with a circle near completion around it. This speed class mark means the sequential write speed for the card, ranging from Speed Class 2, 4, 6, and 10, which respectively means the minimum write speed of 2MB/s, 4MB/s, 6MB/s, and 10MB/s.
Speed Class Minimum Sequential Writing Speed
2 2MB/s
4 4MB/s
6 6MB/s
10 10MB/s


  • UHS Speed Class mark was indicated with a symbol of number inside a U-shaped symbol. U1 means minimum writing speed of 10MB/s, while for U3 shows the card’s with capable writing speed of 30MB/s or higher subsequently which was introduced around the year of 2010 to 2013.
UHS Speed Class  Minimum Sequential Writing Speed
U1 10MB/s
U3 30MB/s
  • Video Speed Class was symbolized with the letter “V” shape followed by a number. The number ranges from 6, 10, 30, 60 and 90 that tells its minimum write speed of 6MB/s, 10MB/s, 30MB/s, 60MB/s and 90MB/s respectively.
Video Speed Class Minimum Sequential Writing Speed
V6 6MB/s
V10 10MB/s
V30 30MB/s
V60 60MB/s
V90 90MB/s

To date, the highest available Video Speed Class is V90 that tells you the card can sequentially write at minimum of 90MB/s or higher. As example when you are are recording 4K video footage, SD Association suggest using any card between 10MB/s to 60MB/s for smoothness video recording. Thus you are good to record 4K footage using the cards with Speed Class 10, U1, U3, V10, V30, or V60.



Application Performance Class

With the newly introduced standard developed by SD Association in the year 2016, symbolized with a letter “A” and next to it is number. This application performance class tells you the card’s minimum random read and random write speeds which were theoretically measured in Input/Output Operations Per Second (IOPS).

Application Performance Class Pictograph (Symbol) Minimum Random Read Minimum Random Write Minimum Sustained Sequential Write
Class 1 (A1)* 800px-SD_App_Performance_1.svg 1500 IOPS 500 IOPS 10MBytes/sec
Class 2 (A2)** 1024px-SD_App_Performance_2.svg 4000 IOPS 2000 IOPS 10MBytes/sec

*The detailed preconditions and test are defined in SD 5.1 Part 1 Physical specification.

**The detailed preconditions and test are defined in SD 6.1 Part 1 Physical specification.

To date, you are looking at two available application performance Class 1 (A1) and Class 2 (A2) standards. For the Class 1 (A1) card are having capability of only recently launched into consumer space as having a minimum random write of 500 IOPS and minimum random read of 1500 IOPS, whereas for Class 2 (A2) card with minimum random write stands higher at 2000 IOPS and minimum random write at 4000 IOPS respectively.

In an actual case, the higher IOPS shown on the cards indeed allow smartphone device users with Android 6.0 (or higher) capable to install apps using Android Adopted Storage feature. In general, if users who used to install apps or games onto the memory card will notice reduced startup loading speed. However for game apps installed on the microSD card was  in fact faster at booting up time on card supports the A1 standard than a regular microSD card.

With this feature, you should also be aware that Android Adopted Storage Encrypts the microSD card and detects it as part of the phone, so when you remove the card which would likely cause issues to the device and refuse to run, until only you reformat the card and reset your phone. So, you should consider when equipped with this benefit and make sure you plan to not remove your microSD from your device.



To conclude on how to buy the right microSD card:

As per explained through the above symbols found on the microSD, you can now identify what are the meanings of the symbols and know what the benefits offer from the card.

Take a look at the table below showing how the SD card specifications have keep advancing over the time:

 SD Specification Evolution history:

Release Year: Specification
2000-2005  Capacity of SD and MicroSD with File System of FAT 12/16, while with Bus Speed of Default Speed (DS) and High Speed (HS)
2006 SDHC and MicroSDHC with File System of FAT32, with Speed Class 2, 4, 6, also comes with combo specification SD Smart and Advance Secure SD.
2009 SDXC and MicroSDXC with File System of exFAT, with Speed Class 10
2010 Bus Speed of UHS-I, SDHC-I, and SDXC-I with UHS Speed Class 1
2011 Bus Speed of UHS-II, SDHC-II, and SDXC-II also come with SMART microSD feature.
2013 UHS Speed Class 3 and iSDIO Wireless LAN SD.
2016 Video Speed Class V6, V10, V30, V60, V90 with Application Performance Class A1.
2017~ Bus Speed of UHS-III, SDHC-III, and SDXC-III also come with App Performance Class 2 and Low Voltage Signal.


So, what microSD card should I get actually?

Up to this moment, it’s proven that the suitable microSD card for your device hugely depends on the type of gadget you are using on.

Take for example, if you are using a 4K action camera such as the GoPro Hero6, it is indeed compatible using up to microSDXC cards that are coming with Class 10 or U1 speeds, and even able using up to maximum capacity of 256GB or even 2TB if available. Such as this specific SanDisk Ultra microSD card would capable to be a good fit.

For instance, you are using smartphone such as  Xiaomi Redmi Note 9, it would only have bare sufficient memory at 32GB onboard storage, however the phone itself capable of using the microSD cards up to 512GB in capacity. This type of phone comes with system of Android 10, thus it is best capable to use the Android Adopted Storage. The suggested is 128GB microSD card with A1 performance class would be a great choice for this phone which allows the user able to operate as many apps as possible from the microSD, instead of having limitation using its small internal storage space. If you prefers to go higher with capacity and be willing to pay more, then just go for it with 512GB storage size without storage limitation.

In contrast, a flagship smartphone user such as the Samsung Galaxy Note10 would go max up to get a 512GB, A1-capable microSD for the device. Yet you may noticed that the Note10’s internal storage capable using UFS 3.0, which able to load apps at faster speed than external storage. The microSD card with speed class 10 or U1 speeds would be sufficient for storage of photos and videos because the phone already has an internal storage of 256GB for apps.

Furnished yourself with the right information, we wish you would able to get a microSD card that is best suited for your device’s need. Feel free to share your thoughts on what favorite brand of microSD card you are loyal to and familiar with in the comments below.


One Response

  1. omega replica watches November 24, 2020

Leave a Reply