FBX (binary) file signature
Magic number at the start of the file · Kaydara FBX Binary
A binary FBX file opens with the ASCII string Kaydara FBX Binary followed by two spaces and a NUL. ASCII FBX files have no such magic and start with a comment or the FBXHeaderExtension token.
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 starts with the bytes 4B 61 79 64 61 72 61 20 46 42 58 20 42 69 6E 61 72 79 (the text Kaydara FBX Binary), it is a FBX (binary) file.
What each byte of 4B 61 79 64 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 |
|---|---|---|---|
| 0 | 4B | 75 | K |
| 1 | 61 | 97 | a |
| 2 | 79 | 121 | y |
| 3 | 64 | 100 | d |
| 4 | 61 | 97 | a |
| 5 | 72 | 114 | r |
| 6 | 61 | 97 | a |
| 7 | 20 | 32 | |
| 8 | 46 | 70 | F |
| 9 | 42 | 66 | B |
| 10 | 58 | 88 | X |
| 11 | 20 | 32 | |
| 12 | 42 | 66 | B |
| 13 | 69 | 105 | i |
| 14 | 6E | 110 | n |
| 15 | 61 | 97 | a |
| 16 | 72 | 114 | r |
| 17 | 79 | 121 | y |
Formats that use the 4B 61 79 64 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 -l 18 example.fbx
- hexdump -C -n 18 example.fbx
- file example.fbx
Windows (PowerShell)
- Format-Hex -Path example.fbx -Count 18
Python
- open("example.fbx","rb").read(18).hex()
In your browser
- Drop the file into the WhatFileType identifier, which reads the signature without uploading it.
Frequently asked questions
What is the FBX (binary) file signature?
FBX (binary) files start with the hex bytes 4B 61 79 64 61 72 61 20 46 42 58 20 42 69 6E 61 72 79 (Kaydara FBX Binary 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 18 example.fbx on Linux or macOS, or Format-Hex -Path example.fbx -Count 18 in Windows PowerShell, and read the first bytes.
Can a file fake the FBX (binary) signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine FBX (binary) file has these exact bytes; a file with the wrong bytes is not really FBX (binary), 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.