YAML MIME Type

About YAML files

YAML only got a registered type in 2024 (RFC 9512). Before that, servers and tools used text/yaml, text/x-yaml and application/x-yaml, and you will still meet all three. Browsers show YAML as text or download it, depending on the type they receive.

Other types seen for these files: text/yaml , text/x-yaml , application/x-yaml . Accept them when reading uploads, but send application/yaml yourself.

File signature

YAML has no fixed signature: it is text without a magic number, so validate uploads by parsing the content rather than by checking bytes.

Serve .yaml with the right Content-Type

Content-Type: application/yaml; charset=utf-8

application/yaml yaml yml;

AddType application/yaml .yaml .yml
AddCharset UTF-8 .yaml .yml

@yaml path *.yaml *.yml
header @yaml Content-Type "application/yaml; charset=utf-8"

curl -sI https://example.com/file.yaml | grep -i '^content-type'
# Content-Type: application/yaml; charset=utf-8

Set the type in code

res.set('Content-Type', 'application/yaml; charset=utf-8');

import mimetypes

mimetypes.add_type('application/yaml', '.yaml')  # if your system doesn't know it
mimetypes.guess_type('file.yaml')[0]  # 'application/yaml'

mime.AddExtensionType(".yaml", "application/yaml; charset=utf-8")
w.Header().Set("Content-Type", "application/yaml; charset=utf-8")

Accept .yaml uploads

<input type="file" accept=".yaml,.yml,application/yaml">

The accept attribute only filters the file picker; users can still choose another file. Listing the extension as well as the type matters, because operating systems don’t always report the type you expect.

Related types

• .json (application/json): JSON
• .xml (application/xml): XML
• .txt (text/plain): Plain text

More data and text

.csv , .tsv , .md , .ndjson , .jsonld , .geojson , .ics , .sql . Look up any extension or type with the MIME type lookup.

Sources

• IANA registration: application/yaml
• MDN: Common media types

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Frequently asked questions