.FST file extension
To open .FST files on Windows, right-click the .FST file → Open with → Choose another app.
To open a .FST file, use “Open with…” (Windows/macOS/Linux) and pick an application that can handle the image/vnd.fst type. If your device can’t preview it (common on mobile), transfer the file to a desktop and try again rather than renaming the extension.
Last updated: April 30, 2026 · Reviewed by Julian Stricker
Open on your device
Choose your operating system for a dedicated step-by-step opening guide.
How to open .FST files
Use these platform-specific instructions to open .FST files safely.
Windows
- Right-click the .FST file → Open with → Choose another app.
- If no app works, check whether your workflow/application suite that produced the file can export it to a common image format (PNG/JPEG/TIFF) and open that instead.
Mac
- Control-click the .FST file → Open With → Other… and try available image/graphics tools.
- If it won’t open, use the originating software (the tool that created the .FST) to export/convert to a standard image format.
Linux
- In your file manager, right-click → Open With and try any installed image/graphics tools.
- If it’s detected as image/vnd.fst but no app is suggested, review your MIME associations (per the MIME Applications spec) or install software from your vendor workflow that supports image/vnd.fst.
iOS
- iOS typically will not preview vendor-specific image formats; if the Files app can’t preview it, transfer the .FST to a desktop OS and open or convert it there.
Android
- Android support is uncommon for vendor image formats; if it won’t open in your file manager, move the file to a desktop OS and use the originating software to export/convert it.
Security notes
- Treat .FST as a binary image format handled by parsers/decoders; malformed image files can sometimes trigger crashes or vulnerabilities in image libraries, so prefer opening in fully updated, reputable software.
- Be cautious with .FST files from untrusted sources, especially if you must install a niche plugin/codec to view them—only install software from a source you trust.
- If you only need to view the content, consider converting using the originating vendor workflow rather than using unknown third-party converters from the internet.
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Can't open this file?
These are the most common causes and fixes when .FST files fail to open.
Common reasons
- The file won’t open or shows “unknown format”
- Linux recognizes the MIME type but no app is offered
- File opens with the wrong program
- The file seems corrupted or partially downloaded
Fix steps
- Try “Open with…” and test any installed graphics or imaging tools you trust.
- If you have the software that created the file, use it to export/convert to PNG/JPEG/TIFF for easier viewing.
- On Linux, confirm the file is identified as image/vnd.fst and then set or install an application association for that MIME type.
OS-specific troubleshooting
What is a .FST file?
.FST maps to the registered vendor image MIME type image/vnd.fst (IANA-registered). In practice, “.fst” indicates a vendor-specific image format, and whether it opens depends on whether your software has a decoder for image/vnd.fst. Linux desktops often rely on shared-mime-info detection and MIME-to-app associations to decide what to use for this type.
Background
The most reliable “ground truth” for .FST in this context is its association with the vendor media type image/vnd.fst in the IANA media types registry. That registration is what many operating systems, libraries, and enterprise tools use to classify the file as an image-like format, even when end-user apps do not advertise explicit “.fst” support.
In institutional MIME mappings, .fst is paired with image/vnd.fst and is sometimes labeled with a vendor/product context (for example, “FAST Search & Transfer ASA” in one published mapping table). This supports the idea that .FST is used in specific vendor workflows rather than being a broadly supported consumer image format.
On Linux desktops, file handling is typically driven by the shared MIME-info database (how the system recognizes types) and the MIME Applications specification (how defaults are chosen). If your system can identify the file as image/vnd.fst but no application claims the type, you’ll see “unknown file type” or be prompted to choose an application manually.
Common MIME types: image/vnd.fst
Further reading
Authoritative resources for more details on the .FST format.
- IANA Media Types Registry (image/*) – includes image/vnd.fst
- Shared MIME-info Database Specification (how Linux detects MIME types)
- MIME Applications Specification (how default apps are chosen per MIME type)
- fileformat.info: image MIME type reference list including image/vnd.fst
- Cisco Crosswork Open Source document (lists image/vnd.fst and extension fst)
Common .FST issues
The file won’t open or shows “unknown format”
Many image viewers don’t include a decoder for image/vnd.fst, so the OS can’t find an application that supports it.
- Try “Open with…” and test any installed graphics or imaging tools you trust.
- If you have the software that created the file, use it to export/convert to PNG/JPEG/TIFF for easier viewing.
- On Linux, confirm the file is identified as image/vnd.fst and then set or install an application association for that MIME type.
Linux recognizes the MIME type but no app is offered
The shared MIME database may detect image/vnd.fst, but no desktop application advertises support for that MIME type, so nothing appears as a default handler.
- Check your desktop’s MIME-to-application associations and add a default for image/vnd.fst if you have a compatible app installed.
- If no compatible app exists, use the producing/vendor toolchain to convert the file to a standard image format.
File opens with the wrong program
If .fst or image/vnd.fst is mis-associated, the OS may route it to an unrelated app.
- Use “Open with…” to pick the correct app and set it as the default for this file type/MIME type.
- Remove or adjust incorrect MIME associations so image/vnd.fst points to your intended viewer/converter.
The file seems corrupted or partially downloaded
Because .FST is uncommon, small file truncations or transfer issues may appear as “unsupported” rather than a clear corruption error.
- Re-transfer or re-download the file and compare file sizes/checksums if available.
- Ask the sender to re-export the image or provide it in a standard format (PNG/JPEG/TIFF) for compatibility.
FAQ
What does .FST most commonly mean here?
In this context, .FST most commonly maps to the IANA-registered vendor image MIME type image/vnd.fst.
Is there a standard MIME type for .FST?
Yes. The IANA registry lists image/vnd.fst, and multiple MIME mapping references pair the .fst extension with image/vnd.fst.
Can I open .FST by renaming it to .png or .jpg?
No. Renaming doesn’t convert the underlying data. Use the software that produced the file or a compatible converter/export option.
Why does my phone/tablet fail to open .FST?
Mobile platforms typically only support common image formats (like PNG/JPEG). Vendor-specific types like image/vnd.fst often require desktop software or the originating workflow to convert/export.
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