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MOBI
What is a MOBI file?
Amazon's older Kindle format. Superseded by AZW3, still what many older files are.
What MOBI is
MOBI is a binary format, meaningful only to a program that knows it. It is used for handing a finished file over.
The extension is .mobi, and the full name is Mobipocket E-book. Both matter less than what the file can hold, which is what the rest of this page is about.
Where MOBI came from
Amazon published it in 2000.
Age is worth knowing here for one practical reason: the older a format is, the more programs have had time to learn it.
The specification belongs to its vendor
Reading it outside the vendor’s own software depends on work done by other people, usually by inspection rather than by documentation. That mostly works and occasionally does not, which is the reason to convert anything you intend to keep.
It has been superseded
The people who made it have moved on, and support is being withdrawn rather than added. Anything still in this format is worth moving while the tools to move it are still around.
It can hold several pages in one file
A MOBI file is not limited to one page, which matters when converting to something that is: a target that holds one image produces one file per page, and the numbering it chooses is worth checking before you send it on.
What opens MOBI
Calibre and Kindle read it, and so do most programs of the same kind.
If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.
Opening it in a browser
No browser reads it.
That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.
It is a delivery format
MOBI is meant to be handed over rather than worked in. Editing one is possible and rarely pleasant; the sane approach is to change the source and export again.
What goes wrong with it
The recurring complaints: support outside its home ground is uneven.
None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.
The facts, in one place
| Extension | .mobi |
|---|---|
| Media type | application/x-mobipocket-ebook |
| Published by | Amazon |
| First published | 2000 |