Memory Cards Reference
Helpful Guide to micro SD cards
The GoPro support website has a list of all the supported micro SD cards. This makes it really easy to find the card that will work with the camera - no second-guessing.
I put together a visual chart of the supported cards. I focused this chart just on the 128GB size cards, as it should be the minimum size card to buy for the GoPro Hero 9.
Here's some reference to all those symbols that you see on the cards.
Video Speed Class - The number following the "V" indicates the minimum number of MB/s the card is capable of sequentially writing. Example: v30 - the card can sustain at least 30MB/s continuous video recording. The V30 is the best Video Speed for 4k/5k videos.
Speed Class - Indicates the minimum writing speed. In this case, it's 10. You may see other cards have 2, 4, or 6. 10 is the best for video recording.
UHS Class Speed - list a UHS class rating to designate the minimum write performance for the card, with U1 indicating 10 MB/s and U3 indicating 30 MB/s or more.
Bus Interface - This indicates the maximum amount of data that can physically move into and out of the card. A II Bus Interface is more powerful and has a second row of pins. Most likely to be supported in the next version of GoPro.
A note about the Micro SD XC - This is the card format and the SDXC is the most popular format as it supports card sizes more than 32GB, up to 2TB. If you need cards bigger than 2TB you'll be looking for a card format that has SDUC.