#file-extension #mime #extension #file-format #format-file


A simple crate for associating MIME types to file extensions

8 stable releases

4.0.1 Feb 18, 2022
4.0.0 Nov 24, 2021
3.0.2 Nov 24, 2021
3.0.1 Sep 24, 2021
2.1.0 Apr 28, 2021

#208 in Filesystem

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16,064 downloads per month
Used in 26 crates (13 directly)

MIT license



Crates.io Unsafe forbidden Build status

This project is a fork of mime_guess. It adds support for many new file formats, uses Rust's 2018 edition, and fixes mime_guess' currently disabled phf-map feature. It has a few other minor changes, but my main reason for creating it is to fix some gaps/issues I've identified with its MIME/extension associations while writing fif.

As of 4.0, the minimum supported Rust version is 1.48. 3.0 can be used if you require support for Rust 1.40. Additionally, as of 3.0, all functions marked as deprecated in mime_guess' 2.0 release have been removed, along with the pub extern crate mime declaration, meaning that you can no longer use new_mime_guess::mime; if you want to use the mime crate, you must add it as a direct dependency.

See the changelog for more information on changes.

The original README is preserved below.

mime_guess GitHub Workflow Status Crates.io

MIME/MediaType guessing by file extension. Uses a static map of known file extension -> MIME type mappings.

Returning Contributors: New Requirements for Submissions Below

Required Rust Version: 1.33



Due to a mistaken premature release, mime_guess currently publicly depends on a pre-1.0 mime, which means mime upgrades are breaking changes and necessitate a major version bump. Refer to the following table to find a version of mime_guess which matches your version of mime:

mime version mime_guess version
0.1.x, 0.2.x 1.x.y
0.3.x 2.x.y

Note: MIME Types Returned Are Not Stable/Guaranteed

The media types returned for a given extension are not considered to be part of the crate's stable API and are often updated in patch (x.y.z + 1) releases to be as correct as possible. MIME changes are backported to previous major releases on a best-effort basis.

Note that only the extensions of paths/filenames are inspected in order to guess the MIME type. The file that may or may not reside at that path may or may not be a valid file of the returned MIME type. Be wary of unsafe or un-validated assumptions about file structure or length.

An extension may also have multiple applicable MIME types. When more than one is returned, the first is considered to be the most "correct"--see below for elaboration.


Adding or correcting MIME types for extensions

Is the MIME type for a file extension wrong or missing? Great! Well, not great for us, but great for you if you'd like to open a pull request!

The file extension -> MIME type mappings are listed in src/mime_types.rs. The list is sorted lexicographically by file extension, and all extensions are lowercase (where applicable). The former is necessary to support fallback to binary search when the phf-map feature is turned off, and for the maintainers' sanity. The latter is only for consistency's sake; the search is case-insensitive.

Simply add or update the appropriate string pair(s) to make the correction(s) needed. Run cargo test to make sure the library continues to work correctly.

Important! Citing the corrected MIME type

When opening a pull request, please include a link to an official document or RFC noting the correct MIME type for the file type in question in the commit message so that the commit history can be used as an audit trail.

Though we're only guessing here, we like to be as correct as we can. It makes it much easier to vet your contribution if we don't have to search for corroborating material.

Multiple MIME types per extension

As of 2.0.0, multiple MIME types per extension are supported. The first MIME type in the list for a given extension should be the most "correct" so users who only care about getting a single MIME type can use the first*() methods.

The definition of "correct" is open to debate, however. In the author's opinion this should be whatever is defined by the latest IETF RFC for the given file format, or otherwise explicitly supercedes all others.

If an official IANA registration replaces an older "experimental" style media type, please place the new type before the old type in the list, but keep the old type for reference:

- ("md", &["text/x-markdown"]),
+ ("md", &["text/markdown", "text/x-markdown"]),

Changes to the API or operation of the crate

We're open to changes to the crate's API or its inner workings, breaking or not, if it improves the overall operation, efficiency, or ergonomics of the crate. However, it would be a good idea to open an issue on the repository so we can discuss your proposed changes and decide how best to approach them.


MIT (See the LICENSE file in this repository for more information.)