Archive Explorer

← All formats

ACE file format

.ace  ·  archive+compression  ·  introduced 1999 by Marcel Lemke

What is a ACE file?

ACE was a 1999 archive format from WinAce that briefly competed with RAR. It is rarely seen today and was removed from many archivers after a 2019 critical vulnerability (CVE-2018-20250) allowed remote code execution simply by unpacking an ACE file. Treat any .ace file with extreme caution.

Most readers reach this page after double-clicking a .ace file and finding their operating system unsure what to do with it. The good news: ACE 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 ACE file

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

On Windows

  1. Locate the .ace 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 .ace 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.ace    # works for almost any format
  3. The files appear in the current directory.

How to create a ACE file

To pack files into a .ace 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 ACE.

On the command line, the canonical create command is:

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

  • Slightly better compression than RAR4 in some cases

Weaknesses and limitations

  • Critical security vulnerabilities
  • Proprietary
  • Effectively obsolete

Typical use cases

  • Legacy Windows archives

Technical details

ACE uses the ACE proprietary algorithm and is identified on disk by the magic byte sequence 2A 2A 41 43 45 2A 2A. The standard MIME type is application/x-ace-compressed. The format is a proprietary specification and is subject to license restrictions for some uses (notably creation).

Frequently asked questions

Is ACE safe to open?

Archive files are containers — they are only as safe as what they contain. A .ace 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 ACE?

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

How does ACE 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.

Related formats