Adinand Auto File Sorter

What format does Android use?

Last reviewed: September 23, 2026 · Markdown version

"Format" means two unrelated things here, and the answer you need depends on which one you are asking. One is the filesystem the storage is formatted with. The other is which kinds of file the phone can open. Both are worth a paragraph; only the second affects how you organise anything.

The filesystem

Android's platform documentation is specific about storage that gets absorbed into the device: "Adopted devices must be formatted with a filesystem that supports POSIX permissions and extended attributes, such as ext4 or f2fs." It also says that when external media is adopted, "it's formatted and encrypted to only work with a single Android device at a time", and spells out the result: "the encryption keys should not be extractable from the parent device, and therefore the storage device can't be mounted elsewhere" (Adoptable storage, read 23 September 2026).

So a memory card set up as internal storage is tied to that one phone. The same page describes the alternative as keeping the card "as-is for simple file storage" — which is why that choice at setup matters more than it looks.

The file types

For media, Android does publish a list. Its supported-formats page describes "the media format support built into the Android platform", and adds that "a particular mobile device might support additional formats or file types that are not listed in these tables" (Supported media formats, read 23 September 2026).

For everything else — PDFs, spreadsheets, archives — opening a file is the job of whichever installed app says it can handle that type. Android's intents documentation describes the mechanism: it is "often important to specify the type of data (its MIME type)", and "Specifying the MIME type of your data helps the Android system find the best component to receive your intent" (Intents and intent filters, read 23 September 2026).

Where the folder structure comes in

Android's storage model is the third thing people mean by "format" — where files are allowed to live. Media and downloaded files sit in shared storage; an app's own app-specific files do not, and Android's storage table answers "Can other apps access?" for them with No (Data and file storage overview, read 23 September 2026). That separation is why "I can see it in this app but not that one" is a normal answer rather than a fault. Scoped storage, explained.

What this means for keeping a phone tidy

You cannot usefully organise by filesystem, and you do not need to. The organisable property is the extension — it is stable, and it is visible. A .pdf is a document whenever it arrived; a folder built on that stays meaningful for years, which is not true of a folder built on dates.

Where Adinand Auto File Sorter fits

Its built-in categories are decided by extension alone. It watches a folder — Downloads by default — and moves what lands there into Downloads › Sorted Files under one of seven categories, using these exact extension lists:

A file with no extension is never sorted, and the app does not read what is inside a file to decide where it goes. On Pro you can add your own rules — an extension list, or a keyword the file name must contain — which is how a category list becomes yours. Android 10 and later, Android only.

Related: What is scoped storage? · Seeing all files on Android · Where documents are stored · Sorting by type and date