What is WMF? Windows Metafile Format Explained
Microsoft's early Windows vector metafile that stores GDI drawing commands for graphics playback.
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What is WMF?
WMF (Windows Metafile) is a graphics file format introduced by Microsoft for Microsoft Windows. It is a metafile, meaning it stores an image as a sequence of drawing instructions rather than a grid of pixels, and it can hold both vector graphics and embedded bitmap data.
A WMF file records a list of Graphics Device Interface (GDI) function calls, the same commands Windows uses to draw to a screen or printer. To display a WMF, an application replays these stored records through GDI. The original format was not device-independent, though optional placeable headers were later added to improve portability.
How WMF Works
A WMF file is a serialized list of GDI records, where each record names a Windows drawing function and its parameters; rendering an image means replaying those records through the Graphics Device Interface in order.[1] Because the instructions are the same calls Windows uses to draw on screen or printer, output scales as vector geometry while embedded bitmaps remain fixed-resolution.[2]
History and Standardization
WMF dates to the early versions of Windows and was long documented only informally; Microsoft later published the MS-WMF open specification describing the record structures in detail.[1] The format and its media type are also registered for interchange, for example in IETF RFC 7903.[3]
Technical Limitations
The original 16-bit metafile was tied to GDI conventions and was not device-independent, so the same file could render at different sizes depending on the target.[2] An optional placeable header carrying a bounding rectangle was added outside the core format to improve portability, a shortcoming later addressed by the 32-bit EMF successor.[2]
MKV Technical Specifications
WMF vs Other Image Formats
| Feature | WMF | SVG | PNG |
|---|---|---|---|
| Type | Vector (metafile)[2] | Vector | Raster |
| Scalability | Yes | Yes | No |
| Origin | Microsoft Windows[1] | W3C | W3C |
| Platform | Windows GDI[1] | Cross-platform | Cross-platform |
| Browser support | None native[3] | Universal | Universal |
| Best for | Legacy Windows clipart | Web vector graphics | Web images |
WMF stores Windows GDI drawing commands for scalable graphics, but its platform dependence makes SVG a more portable vector choice today.
Advantages & Disadvantages
Advantages
As a command list rather than a pixel grid, WMF can describe lines, curves and text compactly and scale them without the pixelation of raster formats.
Because records map directly to GDI calls, Windows and most Windows applications can render WMF without external libraries.
A single WMF can combine vector primitives with embedded bitmap images and limited text, making it flexible for clip art and documents.
Microsoft published the format as the open MS-WMF specification, allowing third-party tools to read and write it accurately.
Disadvantages
The format is tied to the 16-bit Windows GDI model, so it is poorly supported outside Windows and largely superseded by EMF and SVG.
The original WMF lacked a reliable coordinate header, so images could render at unpredictable sizes across devices.
WMF's ability to embed executable-style records has historically been exploited, leading many platforms to restrict or sanitize it.
Common Use Cases
WMF is most often encountered in legacy Windows documents and clip art collections.
Clip art libraries | FileFormer
Microsoft Office and older clip art galleries distributed scalable artwork as WMF files for insertion into documents.
Office document graphics | FileFormer
Drawings and diagrams pasted between older Windows applications were frequently stored on the clipboard and in files as WMF.
Legacy print workflows | FileFormer
WMF was used to spool simple vector graphics to Windows printers via GDI before richer formats became standard.
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Try Image Converter FreeFrequently Asked Questions
Is WMF a vector or raster format?
WMF is primarily a vector metafile that stores drawing commands, but it can also embed raster bitmap data within the same file.
What is the difference between WMF and EMF?
EMF (Enhanced Metafile) is the 32-bit successor to the 16-bit WMF, adding device independence and a richer record set based on the Win32 GDI.
Can WMF files be opened on a Mac or Linux?
Not natively in most cases. Tools such as LibreOffice, Inkscape and ImageMagick can import WMF, but support is less complete than on Windows.
Why are WMF files sometimes blocked?
Because WMF can carry records that older Windows components executed, vulnerabilities led some software to restrict opening untrusted WMF files.
What is a placeable WMF?
A placeable (Aldus) WMF adds a 22-byte header describing the image bounds and units so applications can render it at the correct size.