What Is a .fst File? .fst Format, MIME & How to Open

Quick facts

Extension.fst

File typeFST Image

MIME typeimage/vnd.fst

CategoryImage

Charset—

Compressible—

What is .fst

What is a .fst file?

A .fst file is a FST Image. It is a raster or vector image format used for photos, web assets and design work.

In the mime-db registry it maps to image/vnd.fst. When serving .fst over HTTP, set the Content-Type header as shown in Developer info below.

Related entities: it maps to image/vnd.fst and is used by F* among others — and is delivered over HTTP via the Content-Type header.

How to open .fst files

Use Photoshop or GIMP to open and edit .fst files.
Any text editor (Notepad, VS Code) can inspect the raw content as text.

Developer info

When served over HTTP, responses should set the following header:

Content-Type: image/vnd.fst

Common software that reads/writes .fst:

PhotoshopGIMPPaintPreview

Relation chain

.fstextension of

format

FST Imageserved as

mime type

image/vnd.fstsent via header

http header

Related extensions

Related MIME types

Related programming languages

F*

.fst .fsti

Common uses

Web graphics and photos
Design assets and icons
Print and photography

How to edit .fst files

Open the file with Photoshop, make your changes and save.
Most editors preserve the original formatting and encoding — avoid changing the charset.

How to create .fst files

Create a new file and save it with the .fst extension, or export this format from Photoshop.

Frequently asked questions

What programs can open .fst files?

Common options include Photoshop, GIMP, Paint. You can also open many of these files with built-in viewers or a browser.

How do I create a .fst file?

Create a new file in any text editor or the app that owns the format and save it with the .fst extension.

What is the relationship between .fst and the image/vnd.fst MIME type?

image/vnd.fst is the media type identifier used for .fst files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-08-18

Explore this reference