✏ A little guide to... using SD cards

Android 6 introduced new options for using an SD card in your phone. When you format an SD card or insert a new SD card, you’ll have two options: Internal/phone/adopted storage or external/portable storage. The option that most closely matches older Android versions is the external option.
There are a couple of things to take into account when choosing which option works best for you:

TL;DR: Formatting as internal will allow you to store apps on it and have it encrypted with the system internal storage, whereas formatting as external allows you to have data you can take out of your phone and back in. But formatting it as internal may cause numerous issues with basic features of the phone (camera, storage, audio players, …) and is highly advised against.

  • Formatting as internal storage (:warning: see warning below about such :warning:) means that…

    • your SD card and the internal phone storage will no longer be visible as separate areas in file managers on the phone and in file managers on your computer when you connect it via e.g. MTP and will be considered as a single storage.
    • you have to make a choice where you want your user data (pictures, music, videos, PDFs etc.) to be stored: Internal storage or SD card. This will become the only storage location which is accessible when connecting your phone to a PC. You can move all your data from the phone to the SD card (and back) at any time - as long as there is enough free storage.
    • it may decrease the performance of the phone, as reading/writing the SD-card is slower than the internal storage. If apps are stored on the SD-card this can make them significantly slower.
    • the maximum file size is only limited by the size of the SD card.
    • Android controls where newly installed apps are stored. After installation, many (but not all) apps can be moved from the internal storage to the SD card and vice versa by the user.
    • to remove the SD card, you need to move all your data (user data and apps) back into internal memory first. If the card is removed without going through this process, there will be problems using the phone normally. If you have more data than fits in internal memory, you’ll need to remove data until it does.
    • any data stored on the SD card is encrypted, as it potentially contains sensitive data (app logins etc.). The key used for the encryption is stored in the device. :warning: Factory resetting your phone deletes the key and renders any data on the SD card unreadable (provided nobody finds a practical way of cracking 128bit encryption).
    • :warning: if ever the card or the phone breaks/dies, the data on the other device might be irremediably lost, and for the phone the internal storage broken (which means you may need to do a #dic:hardreset or a reinstallation from scratch) while formatting as external storage allows to access the data independently from the other part

:warning: Formatting the SD card as internal storage on the FP2 (since A10 upgrade), FP3 (since A10 upgrade) and FP4 is confirmed to cause functional and significant storage issues (data loss, empty SD-card, camera unable to shoot photos, etc) often requiring a factory reset. Forum topics here for FP2 (among others), here for FP3 and here for FP4.

If you experience issues after formatting as internal storage, please #contactsupport to report bug and remember to avoid formatting as internal storage whatever your phone model is!

  • Formatting as external storage means that…

    • the SD card will show as a separate folder in your phone.
    • there will be an eject icon to the right of the SD card
    • the SD card can be taken out to be used in other devices, e.g for file transfer
    • data on the SD card is not encrypted, and can be read by anyone who has physical access to the SD card (e.g. when your phone is lost or stolen).
    • the maximum file size is 4 GB, which can be an issue if you want to store movies on the SD card (except if you format it yourself in another format such as exFAT)
    • you can not move apps to the SD card. All apps will be stored in the phone’s internal storage.
    • Android limits the access that apps have to the SD card (as a security feature). Despite these changes having been announced quite a while ago, not all apps have been updated to make use of the new system for requesting access to the SD card. In addition, some apps do not support changing the location for storing data at all (e.g. the pre-installed camera app - alternatives are available). For some other apps, enabling the use of the ‘Storage Access Framework’ will allow access to the SD card (NB: Storage Access Framework is deprecated as of android 11). Apps may still be limited to a folder on the SD card that is created by Android for use by the app - Android/data/app.package.name

How to reformat your SD-card

Open the files app, go in the root location of your SD-card, tap the three dots menu and tap on format.

Phones and SD cards break. Remember to regularly back up your data (to an external device!). Loss of data due to faulty SD-cards is common.

Lists of recommended/compatible SD cards can be found here: