How to Fix Static Files Being Served with the Wrong text/plain Mimetype

python django

I was performing some Python migrations of a Django web app that used to work, and since I switched to Windows 11 on my work machine, the static files were not being served with the correct mimetype application/javascript but rather text/plain.

After some digging into the web app code, I found that the assets were being served using the serve function from django.views.static. Upon checking the Django code, it turns out it does use the mimetypes module to guess the mimetype of the file.

C:\>python
Python 3.12.2 (tags/v3.12.2:6abddd9, Feb  6 2024, 21:26:36) [MSC v.1937 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import mimetypes
>>> content_type, encoding = mimetypes.guess_type("C:\script.js")
>>> print(content_type)
text/plain

On Gnu/Linux machines, mimetypes uses a list of mime.types files

>>> mimetypes.knownfiles
['/etc/mime.types', '/etc/httpd/mime.types', '/etc/httpd/conf/mime.types', '/etc/apache/mime.types', '/etc/apache2/mime.types', '/usr/local/etc/httpd/conf/mime.types', '/usr/local/lib/netscape/mime.types', '/usr/local/etc/httpd/conf/mime.types', '/usr/local/etc/mime.types']

However, on Windows (as of Python 3.2), it uses the Windows registry settings.

C:\>reg query HKCR\.js /v "Content Type"

HKEY_CLASSES_ROOT\.js
    Content Type    REG_SZ    text/plain

So, we need to update the key with the correct mimetype.

C:\>reg add HKCR\.js /v "Content Type" /t REG_SZ /d application/javascript

Let's check now.

C:\>python
Python 3.12.2 (tags/v3.12.2:6abddd9, Feb  6 2024, 21:26:36) [MSC v.1937 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import mimetypes
>>> content_type, encoding = mimetypes.guess_type("C:\script.js")
>>> print(content_type)
application/javascript

All good, now the mimetype is guessed correctly. I hope this helps if you encounter this issue 😄

Clearing out the cobwebs