ACE file signature
Magic number at offset 7 · **ACE**
A WinAce archive carries the ASCII marker **ACE** at byte offset 7, after the header's checksum, size and type fields. It is one of the few common signatures that does not sit at the start of the file, so a test on byte 0 misses it entirely.
What this magic number means
A magic number is a short, fixed run of bytes at a known position that tells a program what a file really is, no matter what the filename says. If a file contains, at offset 7, the bytes 2A 2A 41 43 45 2A 2A (the text **ACE**), it is an ACE file.
The format is best known today for CVE-2018-20250, the unacev2.dll path-traversal flaw that led WinRAR to drop ACE support entirely, so extract old .ace archives only with maintained tools.
ACE was a 1990s rival to RAR and is effectively abandoned, so an unexpected .ace attachment is worth treating with suspicion rather than curiosity.
Sourcing on this one is thin, which is worth saying plainly. The widely copied GCK file signature table has no ACE row at all, so the offset-7 marker rests on Wikipedia's signature list and on the behaviour of tools that still read the format. Treat it as well attested rather than specified: ACE never had a published specification.
What each byte of 2A 2A 41 43 means
Here is the signature byte by byte, the way a hex editor shows it: the position in the file, the value in hex and in decimal, and the character that value stands for in ASCII. Bytes with no printable character show a dot.
| Byte offset | Hex | Decimal | ASCII |
|---|---|---|---|
| 7 | 2A | 42 | * |
| 8 | 2A | 42 | * |
| 9 | 41 | 65 | A |
| 10 | 43 | 67 | C |
| 11 | 45 | 69 | E |
| 12 | 2A | 42 | * |
| 13 | 2A | 42 | * |
Formats that use the 2A 2A 41 43 signature
These file types in our database carry this signature:
How to check a file's signature
You can read the bytes of any file yourself. They are shown in hex, the same way this page lists them.
Linux & macOS
- xxd -s 7 -l 7 example.ace
- hexdump -C -s 7 -n 7 example.ace
- file example.ace
Windows (PowerShell)
- Format-Hex -Path example.ace -Count 16
Python
- f=open("example.ace","rb");f.seek(7);f.read(7).hex()
In your browser
- Drop the file into the WhatFileType identifier, which reads the signature without uploading it.
Frequently asked questions
What is the ACE file signature?
ACE files carry, at offset 7, the hex bytes 2A 2A 41 43 45 2A 2A (**ACE** in ASCII). This magic number identifies the format regardless of the file's name or extension.
How do I check a file's magic number?
Open the file in a hex editor, or run a command such as xxd -l 16 example.ace on Linux or macOS, or Format-Hex -Path example.ace -Count 16 in Windows PowerShell, and read the first bytes.
Can a file fake the ACE signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine ACE file has these exact bytes; a file with the wrong bytes is not really ACE, whatever its name says.
Related signatures
Sources
Reuse this signature
This entry is part of the WhatFileType file signature reference, published under a CC BY 4.0 licence with the full provenance for every entry, a copy-paste embed and a JSON export. Credit WhatFileType and the data is yours to republish.