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EROFS file format

.erofs · .img  ·  compressed read-only filesystem  ·  introduced 2018 by Huawei (mainlined in Linux 5.4)

What is a EROFS file?

EROFS (Enhanced Read-Only File System) is a Linux read-only filesystem developed by Huawei and merged into the kernel in 2018. It is now Android's default system partition format from Android 12 on, replacing ext4 for the read-only system image.

Most readers reach this page after double-clicking a .erofs file and finding their operating system unsure what to do with it. The good news: EROFS is a well-understood format with mature tooling on every major platform. It is supported in one click by mainstream archivers on Windows, macOS, and Linux.

How to extract a EROFS file

Opening a .erofs file is straightforward on every modern operating system. The exact steps depend on which platform you are on:

On Windows

  1. Locate the .erofs file in File Explorer.
  2. Right-click the file. If you have 7-Zip installed, choose 7-Zip → Extract Here. On Windows 11 the built-in extractor handles ZIP, 7z, RAR and several other formats directly through Extract All…
  3. If prompted, pick a destination folder and click Extract.
  4. The extracted files appear in a folder next to the original archive.

On macOS

  1. Find the .erofs file in Finder.
  2. Install The Unarchiver from the Mac App Store, or Keka for both creating and extracting.
  3. Right-click the file → Open With → The Unarchiver (or just double-click after Unarchiver is set as the default).
  4. The extracted folder appears next to the archive.

On Linux

  1. Use your file manager: right-click the archive → Extract Here (file-roller on GNOME, Ark on KDE).
  2. On the command line, run one of: 
    7z x archive.erofs    # works for almost any format
  3. The files appear in the current directory.

How to create a EROFS file

To pack files into a .erofs archive, you typically need an archiver that supports writing this format. Not every tool can create every format — for example, only WinRAR can create real RAR files. The sidebar lists the software known to read and write EROFS.

On the command line, the canonical create command is:

# Use 7-Zip, PeaZip, or the format's reference tool to create .erofs files.

If you regularly create archives at scale, a dedicated archive automation suite can wrap this command in scheduled jobs, integrity checks, and offsite replication.

Strengths

  • Fast random access
  • Better than SquashFS for many small files
  • Mainline kernel

Weaknesses and limitations

  • Read-only
  • Linux-only
  • Newer — older kernels lack it

Typical use cases

  • Android system partition
  • Embedded read-only firmware
  • Container base images

Technical details

EROFS uses the lz4 / lzma algorithm and is identified on disk by the magic byte sequence E2 E1 F5 E0. The standard MIME type is application/octet-stream. The format is an open specification and is free for any use.

Frequently asked questions

Is EROFS safe to open?

Archive files are containers — they are only as safe as what they contain. A .erofs from a trusted source is fine; one received from a stranger can hold malicious executables, scripts, or files engineered to exploit bugs in your archiver. Always keep your archiver updated, and never run unknown executables that come out of an archive. A safe workflow is to extract into a sandbox and scan the contents before opening anything.

What is the maximum file size?

Modern implementations support archives in the multi-terabyte range. The practical limit is your filesystem (FAT32 caps at 4 GB; ext4, NTFS, APFS, and exFAT all comfortably handle multi-TB files).

Can I password-protect a EROFS?

Some archivers can wrap EROFS files in an encrypted container, but the format itself does not always include built-in encryption. Check your archiver's documentation.

How does EROFS compare to other formats?

See our format comparison pages such as ZIP vs 7z, ZIP vs RAR, and tar.gz vs tar.xz for side-by-side feature tables.

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