When I try to insert an image in my post, this message appears at the top of the SE app:

image_mime_type must be set

What does it mean and why does that message appear?

  • SE version: 1.0.85
  • Android Marshmallow
  • MiUi 7

I used the default MiUi gallery.

  • May I know what app did you choose as the image chooser? (e.g. Gallery, Google Photo, Google Drive, etc). Commented May 6, 2016 at 6:00
  • @AndrewT. Done!
    – spund3
    Commented May 6, 2016 at 12:46
  • Did you ever get an answer?
    – Cullub
    Commented Jul 21, 2016 at 19:27
  • 2
    @cullub nope, and the bug is still alive.
    – spund3
    Commented Jul 22, 2016 at 22:41
  • This seems to have happened again.
    – Jason C
    Commented May 13, 2017 at 2:22

2 Answers 2


This is fixed as of version 1.0.93.

We now assume image/jpeg for images where we can't detect a mime-type, and since the error blocking you was just from the API's input validation side, not from the actual image uploader, that fixes it!



I tested it on Android Lollipop (version 5.0.2) and Stack Exchange app version 1.0.92

Steps to recreate the scenario:

I tried to upload a .png file and it was uploaded without an issue. Renaming it to a .jpg or .jpeg file also didn't cause a problem.

However if, for example, I've a file which is named mypetdog.jpg and I rename it to just mypetdog (without any filename extension) and then try to upload it, I get a red banner at the top which says image_mime_type must be set.

Possible issue and fix:

The image you're trying to upload is perhaps missing an extension. Try adding a filename extension to your image, which basically means to change mypetdog to mypetdog.jpg or something equivalent.

  • Thank you so much for the repro step! Commented May 17, 2017 at 21:48

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