.dmg
Disk images · application/x-apple-diskimage
Opens with
A whole disc captured as one file. Open it and it mounts just like the original disc.
| MIME type | application/x-apple-diskimage |
|---|---|
| Category | Disk images |
| Opens in a browser | No |
| Plain text | No |
| Registered type | Unofficial (x-) |
How to read this
- An extension is a label, not the contents. Rename a file to .png and if the bytes inside are JPEG, it is still a JPEG.
- A MIME type is how the internet names a file kind. Browsers look at that value, not the extension, to decide whether to display or download.
- A MIME type starting with x- was never registered as a standard. Plenty are in wide use, but they are not official names.
- Video extensions name a container. The same .mp4 may play on one device and not another, depending on the codec inside.
Frequently asked questions
Q. What is a .dmg file?
It belongs to the disk images category and its MIME type is application/x-apple-diskimage. The contents are binary, so opening it in a text editor shows garbage.
Q. What opens a .dmg file?
Finder, DiskImageMounter all handle it. In a browser it does not display — the browser downloads it instead.
Q. What is the MIME type of .dmg?
application/x-apple-diskimage. The first half, application, names the broad kind; the second half, x-apple-diskimage, names the exact format. It starts with x-, which means it was never registered as a standard.
Q. Can I convert a .dmg file to another format?
Yes — open it and re-save through a converter. Renaming alone changes only the label; the bytes stay put, and programs that check the real format may refuse to open it.
Q. My .dmg file will not open.
First check that Finder is installed. If it still fails, the download may have been cut short, or the file may only be named .dmg while holding a different format inside.