CONVERT
WMF → ICO
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Fast, secure WMF to ICO conversion. No registration required.
WMF is a raster image format with its own balance of compression, colour depth, and software support. That is why users land on this page looking for a ICO copy. Converting WMF to ICO swaps one image container for another without leaving the image family. The choice usually comes down to compatibility with the tool or platform that will consume the file next — some editors handle ICO natively while WMF still requires a plugin or extra step. KaijuConverter re-encodes in the browser session with ImageMagick, preserving resolution and colour profile, and leaves the source WMF untouched. Context: WMF is a raster image format with its own balance of compression, colour depth, and software support. ICO is the Windows icon container with multiple resolutions packed into one file.
Windows Metafile
Source formatWMF (Windows Metafile) is a legacy Windows vector graphics format.
ICO Icon
Target formatICO is the icon file format used for favicons and Windows application icons. A single ICO file can contain multiple image sizes and color depths for different display contexts.
Why convert WMF to ICO
Both WMF and ICO describe a grid of pixels — the difference lies in how that grid is compressed, whether transparency is supported, and which software opens it natively. Moving from WMF to ICO is worth it when the ICO ecosystem is broader for your use case, or when ICO compresses photographs more efficiently than WMF.
HOW TO CONVERT
WMF → ICO
Drop the WMF file
Drag and drop or click to upload your WMF. The image is transferred securely over HTTPS and queued for conversion.
Re-encode with ImageMagick
ImageMagick decodes every pixel of the WMF and writes a matching ICO with sensible default quality settings.
Download the ICO
The converted ICO is ready to download as a single file; both files delete automatically within two hours.
Common Use Cases
Share across platforms
Send ICO files to anyone without worrying about whether they have the right software for WMF.
Embed in documents
Drop ICO output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
ICO often produces smaller files than WMF for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
WMF vs ICO — Strengths and limitations
What each format does best, and where it falls short.
WMF Strengths
- Native Windows vector format.
- Efficient for line-art and diagrammatic images.
- Preserved in Office clipboard workflows.
Limitations
- Windows-only — poor Mac and Linux support.
- 2005 security vulnerability eroded trust.
- 16-bit coordinates in original WMF limit canvas size.
ICO Strengths
- Multi-resolution: one file, many sizes, OS picks the right one.
- Universal favicon support in every browser since IE5.
- Supports transparency (1-bit since 1985, full alpha since XP).
- Tiny file size — an entire favicon pack typically fits in under 15 KB.
- No licensing or patent concerns — fully in the public domain spec-wise.
Limitations
- Cannot compress continuous-tone images efficiently — use PNG or WebP for photos.
- Format is essentially frozen in 1999 — no HDR, no wide gamut, no modern features.
- Maximum image dimension is 256×256 px (inside an ICO container).
WMF vs ICO — Technical specifications
Side-by-side comparison of the technical details.
WMF
- MIME type
- image/wmf
- Extension
- .wmf
- Container
- Sequence of GDI drawing records
- Successors
- .emf (1993), .emf+ / .emfx (2000)
- Related spec
- [MS-WMF] (Microsoft Open Specifications)
ICO
- MIME type
- image/vnd.microsoft.icon
- Max resolutions per file
- 65 535 images
- Max single image size
- 256×256 px
- Color depths
- 1, 4, 8, 24, 32 bits per pixel
- Compression
- Uncompressed bitmap or embedded PNG (Vista+)
| Specification | WMF | ICO |
|---|---|---|
| MIME type | image/wmf | image/vnd.microsoft.icon |
| Extension | .wmf | — |
| Container | Sequence of GDI drawing records | — |
| Successors | .emf (1993), .emf+ / .emfx (2000) | — |
| Related spec | [MS-WMF] (Microsoft Open Specifications) | — |
| Max resolutions per file | — | 65 535 images |
| Max single image size | — | 256×256 px |
| Color depths | — | 1, 4, 8, 24, 32 bits per pixel |
| Compression | — | Uncompressed bitmap or embedded PNG (Vista+) |
WMF vs ICO — Typical file sizes
Approximate file sizes for common scenarios.
WMF
- Simple clipart 5-50 KB
- Detailed vector drawing 50-500 KB
ICO
- Classic favicon (16×16 only) < 2 KB
- Multi-size favicon pack (16/32/48/256) 5-15 KB
- Full Windows app icon set 20-100 KB
Quality & Compatibility
If ICO is a lossless format (PNG, TIFF, BMP) the output keeps every pixel of the decoded WMF exactly. If ICO is a lossy codec (JPEG, WebP, HEIC), the encoder re-compresses the image at the quality level you select — default 85 is transparent for photographs, quality 92+ for illustrations with hard edges.
Tips for Best Results
- Keep the original WMF alongside the ICO output — re-encoding already-lossy images accumulates detail loss on each round.
- If the ICO will be uploaded to a CMS, check whether the platform has a max dimension and downscale once on export rather than letting the CMS resize automatically.
- For thumbnails and avatars, export the ICO at exactly the display size; browsers will otherwise resample and the image may look soft.
Frequently Asked Questions
It depends on the codecs involved. If both WMF and ICO are lossy, the pixels are re-encoded and a small amount of detail is discarded — invisible at default quality settings on photographs. If ICO is lossless (PNG, TIFF, BMP) the output keeps every pixel of the decoded WMF exactly, but cannot recover detail that WMF had already compressed away.
Often yes, especially when ICO is lossless. WMF tuned for efficient web delivery will usually produce smaller files than ICO's default settings. If file size matters, drop the quality in Advanced or pick a more compressed target format instead.
KaijuConverter uploads over HTTPS, processes the image in an isolated container and deletes both the source and the output within two hours. No account is required, file contents are never logged, and we do not use uploads to train any model. For confidential material, the paid plan includes a data-processing agreement.
Related comparisons
See these formats side by side to understand which fits your use case best.
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Read guideSecure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.