WMZ File Documentation

Summary

A WMZ file is a Windows Media Player skin: a ZIP package that holds the graphics and script defining a custom look for the player. Its MIME type is application/x-ms-wmz. Double-click it and the legacy Windows Media Player loads it through the Skin Chooser and switches into skin mode. This is a legacy Windows feature: the modern Media Player app in Windows 11 does not use WMZ skins. Install skins only from sources you trust, because the package can contain JScript the player runs.

Technical details

FeatureValue
Full nameWindows Media Player Skin (compressed)
File extension.wmz
MIME typeapplication/x-ms-wmz
Format typeZIP archive containing a skin definition, art and script
Container / base formatZIP (PKZIP)
DeveloperMicrosoft
IntroducedWindows Media Player 7 (2000)
Open standardNo (skin format); ZIP container is an open format
Byte orderLittle-endian (ZIP structures)
Magic number (hex)50 4B 03 04 (“PK”, ZIP local file header)
Skin definition.wms file inside (XML-like markup)
Art assetsBMP / PNG / JPG bitmaps
ScriptingJScript, run by the player when the skin loads
Applied byWindows Media Player (Legacy) Skin Chooser
Windows 11 supportNo — the modern Media Player app dropped skins
Inspect withRename to .zip or open in 7-Zip
Related extensions.wms, .zip, .wsz (Winamp, different), .emz
Specificationlearn.microsoft.com (WMP skins); PKWARE APPNOTE (ZIP)
File signature (magic bytes)
50 4B 03 04

Offset 0, 4 bytes. This is the ZIP local file header signature, ASCII PK (50 4B) followed by 03 04: a WMP skin .wmz is simply a ZIP archive. Because of this, renaming the file to .zip, or opening it directly in 7-Zip, lets any archive tool list and extract its contents (the .wms skin definition, bitmap art and JScript). A truncated or non-ZIP .wmz may instead be a GZIP-compressed image (see the FAQ).

What is a WMZ file?

A WMZ file is a Windows Media Player skin: a compressed package that replaces the standard player interface with a custom design, giving it a different shape, buttons and layout. Microsoft introduced the format with Windows Media Player 7 in 2000, during the era when skinning media players was a popular customisation hobby. Under the hood a .wmz is nothing exotic: it is a ZIP archive, so it begins with the bytes PK (50 4B 03 04), that bundles together the files a skin is made of. Many old .wmz skins still circulate on download archives.

The important practical point is that WMP skinning is a legacy feature. The classic Windows Media Player, still available as the “Windows Media Player Legacy” app, loads .wmz skins, but the redesigned Media Player app that ships with Windows 11 does not. A downloaded skin therefore applies only to the old player, which is the usual reason a .wmz “does nothing” when double-clicked on Windows 11.

Inside the package: .wms, bitmaps and JScript

Because a .wmz is a ZIP archive, you can rename it to .zip (or open it directly in 7-Zip) and see exactly what a skin is built from. Three kinds of content make up the package.

ComponentWhat it is
.wms skin definitionAn XML-like markup file describing the interface: the layout, the controls, and how regions map to player functions
Bitmap artBMP, PNG or JPG images that draw the player’s shape, buttons and states
JScriptScript that wires up control behaviour and player actions when the skin is loaded

The .wms file is the heart of the skin. Its markup declares the visible elements (buttons, sliders, text, the video region) and binds each to a player command or property. The bitmaps supply the artwork, often with separate images for a control’s normal, hover and pressed states, plus a mask image that defines the non-rectangular outline of the player window. The JScript adds interactive logic that the markup alone cannot express. This is also how skins were authored: you write the .wms markup and script, draw the bitmaps, ZIP them together, and rename the archive to .wmz.

Applying a skin: the Skin Chooser and skin mode

To use a skin, you double-click the .wmz. The legacy Windows Media Player loads it into its Skin Chooser, the gallery of installed skins, and when you choose Apply Skin the player switches from its full mode into skin mode, drawing the custom interface in place of the default one. Skin mode is a compact, reshaped window; the player can be switched back to full mode from a control the skin exposes or from the taskbar. Because this whole path lives in the legacy player, it is unavailable in the Windows 11 Media Player app, which has no Skin Chooser and no skin mode. To use old skins you install the Windows Media Player Legacy app, which still ships as an optional feature.

One extension, two file types

The .wmz extension has a second, unrelated meaning worth knowing about, because it changes what tool you reach for. Besides the Windows Media Player skin described here, .wmz was also used for a compressed Windows Metafile: a WMF vector image packed with GZIP, the sibling of the .emz (compressed EMF) format that old Microsoft Office clip art used. The two are told apart by their first bytes. A skin is a ZIP and starts with PK (50 4B); a compressed metafile is GZIP and starts with 1F 8B. If your .wmz is clip art rather than a player skin, extract the .wmf inside with 7-Zip and open it in an image viewer; that is a different file type with its own toolchain, not a Media Player skin.

Frequently asked questions

How do I install a Windows Media Player skin (.wmz)?

Double-click the .wmz to load it into the legacy Windows Media Player Skin Chooser, then choose Apply Skin. The Windows 11 Media Player app does not support WMZ skins; only the legacy player does.

Why won’t my .wmz skin apply on Windows 11?

The redesigned Media Player app in Windows 11 dropped skin support. Install the “Windows Media Player Legacy” app, still available as an optional feature, to load .wmz skins.

What is inside a .wmz skin file?

A ZIP package containing a .wms skin-definition file (the interface markup), bitmap images, and JScript. Rename it to .zip or open it with 7-Zip to see the contents.

My .wmz is not a skin. Could it be an image?

Possibly. The .wmz extension is also used for a compressed Windows Metafile, a GZIP-packed WMF clip-art image that starts with the bytes 1F 8B rather than PK. If yours is clip art, extract the .wmf with 7-Zip and open it in an image viewer.

References