YAML MIME type is not correct

[Omikhleia]

Greetings,

I'm interested in using this library in a small project, where I'll also need to get the correct MIME type for YAML files.

Observed

> mimetypes = require 'mimetypes'
> mimetypes.guess("file.yml")
text/yml
> mimetypes.guess("file.yaml")
text/yaml

Expected

As of 2025, I would have expected application/yaml.
(BTW. I don't know what text/yml is supposed to be, vs. text.yaml)

Rationale:

Historically, YAML was supposedly referenced as (mostly) application/x-yaml, or (sometimes) as text/yaml or text/x-yaml.

It took more than 22 years for YAML to be recognized, but in early 2024 it was finally officially registered, see RFC9512

• The official MIME type is application/yaml.
• Older (used by non-registered) aliases application/x-yaml, text/yaml, and text/x-yaml are deprecated.
• The RFC states the usual file extensions are yaml (preferred) and yml, see 3.3.
• (The +yaml suffix is also registered, but that's not relevant for the discussion here)

[Omikhleia]

For reference, the pythonesque mimetypes.py (referred in the README as an original source initially) was also updated in early 2025, to take into account this MIME type for both .yaml and .yml files.

[Tieske]

We're now collecting the list from https://svn.apache.org/repos/asf/httpd/httpd/trunk/docs/conf/mime.types, so no longer from mimetypes.py. The apache list hasn't been updated yet though.

Since the yaml one isn't in the list, this library carried some overrides, see https://github.com/lunarmodules/lua-mimetypes/blob/main/mimetypes/extensions.lua (this is where yml and yaml are defined).