RealMedia file signature
Magic number at the start of the file · .RMF
RealMedia files, both .rm and the variable-bitrate .rmvb, begin with the four ASCII bytes .RMF, the RealMedia File header chunk. The streaming-era container then continues as a series of tagged chunks.
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 2E 52 4D 46 (the text .RMF), it is a RealMedia file.
Formats that use the 2E 52 4D 46 signature
These file types in our database carry this signature:
How to check a file's signature
You can read the first bytes of any file yourself. The magic bytes are shown in hex, the same way this page lists them.
Linux & macOS
- xxd -l 16 example.rm
- hexdump -C -n 16 example.rm
- file example.rm
Windows (PowerShell)
- Format-Hex -Path example.rm -Count 16
Python
- open("example.rm","rb").read(4).hex()
In your browser
- Drop the file into the WhatFileType identifier, which reads the signature without uploading it.
Frequently asked questions
What is the RealMedia file signature?
RealMedia files start with the hex bytes 2E 52 4D 46 (.RMF 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.rm on Linux or macOS, or Format-Hex -Path example.rm -Count 16 in Windows PowerShell, and read the first bytes.
Can a file fake the RealMedia signature?
Renaming a file does not change its bytes, so the extension can lie but the signature usually cannot. A genuine RealMedia file has these exact bytes; a file with the wrong bytes is not really RealMedia, whatever its name says.