What is a .ace file?
WinAce Compressed Archive · Archive · Marcel Lemke (e-merge) · 1998
An .ace file is a WinAce archive, a late-1990s rival of RAR and ZIP that compressed slightly better at the time. The format is proprietary, WinAce is abandoned, and ACE support was dropped from most tools.
What is a .ace file used for?
ACE had a real following around 2000 thanks to strong compression, but it never opened its specification, and development stopped. The marker bytes **ACE** sit at offset 7 of the header rather than at the start of the file.
The format's afterlife is a security story: in 2019 the unacev2.dll library that nearly every unpacker used to read ACE turned out to have a path-traversal flaw (CVE-2018-20250), after which WinRAR simply removed ACE support. Extract old archives with a current, patched tool only.
What opens a .ace file?
The .ace format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- 7-Zip (via plugin) or WinRAR 5.61 and older (not recommended)
- PeaZip
macOS
- The Unarchiver
Linux
- unace (nonfree package)
Open a .ace file step by step
- Confirm the file really is a .ace. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with 7-Zip (via plugin) or WinRAR 5.61 and older (not recommended) or PeaZip.
- On Mac, use The Unarchiver.
- On Linux, try unace (nonfree package).
- Still stuck? Convert the .ace to zip, which opens more widely.
Why can't I open my .ace file?
Almost always because no installed app understands ACE. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .ace at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .ace file
You can convert a .ace file to zip, 7z using a conversion tool or the export menu of an app that opens it.
What is the .ace file signature (magic bytes)?
A .ace file carries the hex bytes 2A 2A 41 43 45 2A 2A at offset 7, which read as **ACE** in ASCII. Programs identify ACE by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for ACE. For a full breakdown, see the ACE file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| 2A 2A 41 43 45 2A 2A | 7 | **ACE** | **ACE** marker |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .ace file?
An .ace file is a WinAce archive, a late-1990s rival of RAR and ZIP that compressed slightly better at the time. The format is proprietary, WinAce is abandoned, and ACE support was dropped from most tools.
How do I extract an .ace file today?
On Windows, PeaZip handles most ACE archives; on macOS, The Unarchiver; on Linux, the unace utility. Repack anything you keep as ZIP or 7z.
Why did WinRAR remove ACE support?
Because of CVE-2018-20250: the bundled unacev2.dll could write files outside the extraction folder (into Startup, for example). WinRAR 5.70 dropped the DLL entirely.
Is the ACE format still used?
No. WinAce is abandoned and no modern archiver creates ACE files, so the extension only appears on old downloads and backups.
Related formats
Sources
Details on this page were checked against authoritative references. How sources are ranked and what is deliberately left out is set out in the methodology.