How do I set the Content-Type for .m4a in Nginx?

Make sure audio/mp4 m4a; is listed in the types block (usually in /etc/nginx/mime.types) and reload Nginx.

Should I gzip .m4a files?

No — the format is already compressed, so HTTP compression gives no benefit.

.m4a MIME Type — audio/mp4

audio/mp4

MIME type for .m4a

Audio

What is the MIME type of .m4a files?

The MIME type (media type) for MPEG-4 audio (AAC) files with the .m4a extension is audio/mp4. AAC audio in an MP4 container, used by Apple Music and many podcasts.

Content-Type header

Content-Type: audio/mp4

Server configuration

Server	Configuration
Nginx (`mime.types` or `types {}`)	`audio/mp4 m4a;`
Apache (`.htaccess`)	`AddType audio/mp4 .m4a`
IIS (`web.config`)	`<mimeMap fileExtension=".m4a" mimeType="audio/mp4" />`
Node.js / Express	`res.type('m4a')` or `res.setHeader('Content-Type', 'audio/mp4')`
Amazon S3	Set `Content-Type: audio/mp4` on the object (metadata), or pass `--content-type audio/mp4` to `aws s3 cp`

Should .m4a files be compressed?

No. MPEG-4 audio (AAC) files are already compressed internally, so gzip or Brotli would waste CPU and barely reduce — sometimes even increase — the size. Leave audio/mp4 out of your compression configuration.

Why the MIME type matters

Browsers decide what to do with a response — render, run, play or download — from the Content-Type header, not the file extension. With X-Content-Type-Options: nosniff, a wrong type causes stylesheets and scripts to be blocked outright. For uploads, never trust the type sent by the client; check the file’s content (its magic bytes) on the server.

.m4a MIME Type: audio/mp4