What is an SD Card?
An SD card, or Secure Digital card, is a non-volatile memory card format developed by the SD Association for use in portable devices such as digital cameras, smartphones, and tablets (https://en.wikipedia.org/wiki/SD_card). The SD format was introduced in 1999 and has become the most popular card format for consumer electronics.
SD cards are small, removable flash memory cards that retain data without power. They are used for storage and transfer of photos, videos, music, documents, and other files. There are several types of SD cards that vary by capacity and speed (https://www.pcmag.com/encyclopedia/term/sd-card).
Common types of SD cards include SD, SDHC (high capacity), SDXC (extended capacity), microSD, and miniSD. SD cards offer capacities ranging from 1 GB to 2 TB. Speeds range from default Speed Class 2 up to UHS Speed Class 3 for fast transfer of full HD videos.
Because of their small size, portability, and storage capacity, SD cards are commonly used in cameras, smartphones, tablets, handheld gaming devices, laptops, drones, dash cams, and more. They provide removable storage to save photos, videos, music, apps, and other data.
Why Use SD Cards with Android?
Using SD cards with Android devices provides several key benefits that make them a popular storage option. Some of the main reasons to use SD cards include:
Expand storage – SD cards allow you to dramatically increase the available storage on your Android device. Many Android phones and tablets start with limited onboard storage, so adding an SD card lets you store more apps, photos, videos, music and other files. With SD cards now available up to 1TB, you can carry a huge amount of extra storage in your pocket.1
Keep media separate – Storing music, movies, photos and other media on an SD card keeps that content separate from apps and the operating system on the device’s internal storage. This separation can make it easier to manage files and transfer media between devices.
Transfer files between devices – The removable nature of SD cards makes transferring files a breeze. You can remove the card from your Android device and plug it into your computer to transfer files back and forth. Want to load up a new SD card with movies and music for a road trip? No problem. SD cards make ideal transportable storage.
Formatting SD Cards for Android Use
SD cards need to be properly formatted before they can be used with Android devices. There are some key differences between formatting the card on a computer versus directly on the Android device:
- Formatting on Android allows you to choose between FAT32, exFAT, and in some cases NTFS file systems. Formatting on a computer typically only gives you the option for FAT32 or exFAT.
- Formatting on the phone lets you set the SD card as internal storage and migrate apps and data. This isn’t possible when formatting on a computer.
- Directly formatting on Android tailors the card specifically for that device’s needs and OS version. Formatting on a computer doesn’t optimize the card.
FAT32 is compatible with all Android devices but only supports up to 32GB cards. exFAT works with cards up to 2TB but may not be supported on older Android versions. NTFS offers advanced features but isn’t widely compatible (1).
To format on Android, go to Settings > Storage and tap the SD card name. Choose “Format” or “Format as internal” if available. Pick FAT32, exFAT or NTFS and confirm formatting. This will erase all data on the card.
Setting SD Card as Default Storage
Android allows you to set your SD card as the default storage location for apps, photos, videos, and other media files. This allows you to store more data on your SD card rather than filling up your phone’s internal storage. To set your SD card as default storage:
Open the Settings app and go to Storage. Under Portable storage, select your SD card. Tap the three dots in the top right corner and choose Storage settings.
Toggle on ‘Use as internal storage.’ This will allow your phone to fully integrate the SD card and treat it like built-in storage. Apps, photos, videos and other files will automatically save to the card by default.
You can also set individual defaults here for apps, photos, videos, audio and downloaded files. Choose your SD card as the default location for each media type.
For more advanced users, you can use ADB commands to force particular apps or services to use the SD card rather than internal storage. Connect your Android phone to a computer and use ADB shell commands like:
pm set-install-location 2
This will set the default install location to be your SD card for all future app installs and updates.
With your SD card set as internal storage, your phone will store all data possible on the card rather than filling up the internal memory. Just make sure to back up important files, as the SD card can be removed.
Moving Apps to SD Card
One of the main benefits of using an SD card with an Android device is being able to move apps from the phone’s internal storage to the SD card. This frees up the limited internal storage for other data and media. There are a few ways to move apps to the SD card on Android.
The easiest method is to use the built-in App Info or App Manager in your Android’s Settings. Go to Settings > Apps & Notifications > App Info/Manager, select the app you want to move, and tap the “Change” button to set the SD card as the default install location [1]. This will move the app and its data to the SD card. However, not all apps support this feature and will be grayed out [2].
Third-party app manager apps like AppMgr III or Link2SD can forcefully move unmovable apps to the SD card by partitioning the card and using complex linking. However, this may cause instability and app crashes. Also, moving an app to the SD card often prevents updating it from the Play Store.
Adoptable storage allows an SD card to be formatted and encrypted to act as internal storage. Apps can seamlessly be installed to adoptable storage without limitations. However, you lose the ability to easily remove and exchange the card. Data transfer speeds may also be reduced.
In summary, moving apps to an SD card allows you to free up internal storage. But some limitations remain, so it’s not a seamless experience. Carefully consider if you want to dedicate the SD card to adopted internal storage versus exchangeable portable storage.
Transferring Files Between Phone and SD Card
There are a couple main ways to transfer files between your Android phone’s internal storage and an SD card. The easiest method is to use a file manager app on your phone. Apps like Files by Google and ES File Explorer allow you to easily copy, move, and manage files between internal storage and inserted SD cards.
To transfer files using a file manager app, open the app and navigate to either your phone’s internal storage or the SD card. You can then long press on files or folders to select them, and use options like “Copy to” or “Move to” to transfer the files between locations. Most file manager apps also let you batch select multiple files and entire folders for quick transferring.
Another option is to connect your Android phone to a computer via USB and use your computer’s file explorer to transfer files back and forth. When connected, the phone’s storage and SD card show up as external drives on the computer. You can then drag and drop files between the computer and Android device storage as you would with any other external drive.[1]
Some Android devices also support wireless transfers over a local network using apps like AirDroid. This allows wireless file management without any cables.
SD Card Corruption and Recovery
SD cards can become corrupted over time, leading to issues like inability to read or write data, missing files, and more. There are several potential causes of SD card corruption on Android devices:
– Sudden removal of the SD card before properly unmounting it can lead to file system errors.[1]
– Improper shutdowns or restarting the phone while writing data to the card can corrupt data.[2]
– Physical damage from drops, humidity, high heat, or magnetic interference can render data unreadable.
– Software bugs or malware attacks may also corrupt data.
To fix a corrupted SD card on Android without losing data, there are a few options to try:
– Remove and re-insert the SD card to remount it. This may resolve simple errors.[3]
– Use Android’s built-in Disk Utility app to run a diagnostic scan and attempt repairs.
– Connect the SD card to a PC and run CHKDSK /f to scan and fix file system errors.[4]
– Use data recovery software to extract photos, videos, and other files from the corrupted card before reformatting it.
While corrupted cards can often be fixed, it’s a good idea to regularly back up important data as a precaution against permanent data loss.
Improving SD Card Performance
One way to improve SD card performance is to get a card with a higher Speed Class rating. SD card Speed Classes range from 2 to 10, with higher numbers indicating faster performance. Class 10 cards offer maximum transfer speeds of at least 10MB/s, making them ideal for demanding tasks like recording 4K video.
You can also optimize your SD card’s read and write speeds through some simple software tweaks. For example, increasing the “read_ahead_kb” value allocates more memory for read-ahead caching, resulting in faster read speeds. One study showed that increasing this value from its default of 128KB to 1024KB improved read speeds by 100-200% [1]. Just be careful not to set the value too high, as that can have the opposite effect.
Some other tips for faster SD card performance on Android include:
- Moving apps to internal storage instead of SD card
- Using an SD card optimization app like SD Card Speed Increase
- Regularly checking for errors and optimizing the SD card
- Updating to the latest OS version for performance improvements
While SD cards will never be as fast as internal storage, a few simple tweaks can dramatically boost their performance on Android.
SD Card Security and Encryption
SD cards can pose security risks if you have sensitive personal data stored on them. Unlike internal phone storage, removable SD cards are easy to misplace or have stolen. However, Android offers encryption options to protect your data.
Starting in Android 5.0 Lollipop, you can encrypt external SD cards. Encryption scrambles data on the card so that it can only be accessed with a password or PIN. To enable SD card encryption, go to Settings > Security > Encrypt SD card. This will encrypt the entire card, so make sure you have backups of any data already on it.
Some Android devices also support encrypting SD cards used as internal storage. Adoptable storage allows you to format the SD card and integrate it with internal storage. When enabled, Android will automatically encrypt the card. However, adoptable storage has downsides like reduced SD card portability.
Third-party apps like DroidFS [1] also enable manually encrypting an SD card while still using it as portable storage. This allows selective encryption of folders rather than the entire card.
Overall, encrypting your SD card provides an additional layer of security against physical theft or loss. Just make sure to remember the password, or the data will be inaccessible.
When to Use MicroSD vs Portable SSD
Both MicroSD cards and portable SSDs have advantages and disadvantages that make them better suited for certain use cases with Android devices.
Some pros of using MicroSD cards are:
- Low cost – You can get high capacity MicroSD cards very affordably these days.
- Removable/transferable – MicroSD cards can easily be removed, swapped between devices, and used to transfer files.
- Wide compatibility – Most Android devices have MicroSD slots, so compatibility is rarely an issue.
However, the cons of MicroSD cards include:
- Slower speeds – MicroSD cards have much lower read/write speeds compared to SSDs. This can impact performance when running apps or loading large files.
- Less reliable – MicroSD cards are more prone to corruption and failures over time compared to SSDs.
- Not as durable – MicroSD cards are small and fragile, making them easier to damage compared to encased SSDs.
The pros of using a portable SSD include:
- Faster speeds – SSDs have much higher read/write speeds, which improves performance.
- More reliable – SSDs are less prone to corruption and failures.
- More durable – The encased design protects the components from damage.
The downsides of a portable SSD:
- Higher cost – You pay more per gigabyte compared to MicroSD cards.
- Not built-in – Requires carrying around an external device and cable.
- Compatibility issues – Some older Android devices don’t support SSDs over USB.
In general, MicroSD cards work best for offline media storage and accessing files that don’t require fast speeds. Portable SSDs are ideal for running apps, gaming, or working with large files that benefit from higher speeds and reliability.