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WMV
What is a WMV file?
Microsoft's video format. Common in older corporate archives, awkward outside Windows.
What WMV is
WMV is a container: a wrapper that holds streams encoded by something else. It is used for handing a finished file over.
The extension is .wmv, and the full name is Windows Media Video. Both matter less than what the file can hold, which is what the rest of this page is about.
Where WMV came from
Microsoft published it in 1999.
A format that has been readable for that long is a format worth trusting with something you want back in ten years.
The specification belongs to its vendor
Reading it outside the vendor’s own software depends on work done by other people, usually by inspection rather than by documentation. That mostly works and occasionally does not, which is the reason to convert anything you intend to keep.
It has been superseded
The people who made it have moved on, and support is being withdrawn rather than added. Anything still in this format is worth moving while the tools to move it are still around.
WMV is a box, and the codec is what is in it
It usually holds WMV9 and VC-1. This is the distinction behind most "why will this not play" questions: two files with the same extension can contain entirely different encodings, and a player that refuses one may be perfectly happy with the other.
It also explains why changing container is often fast and lossless while changing codec is neither. Moving the same stream into a different box rewrites the box; re-encoding rewrites the picture.
What else it can carry
WMV can hold several audio tracks.
That matters mostly when converting: whatever the target cannot hold is dropped, usually without a warning.
What opens WMV
Windows Media Player and VLC read it, and so do most programs of the same kind.
If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.
Opening it in a browser
No browser reads it.
That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.
It is a delivery format
WMV is meant to be handed over rather than worked in. Editing one is possible and rarely pleasant; the sane approach is to change the source and export again.
What goes wrong with it
The recurring complaints: support outside its home ground is uneven.
None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.
The facts, in one place
| Extension | .wmv |
|---|---|
| Media type | video/x-ms-wmv |
| Published by | Microsoft |
| First published | 1999 |