.mobi — Mobipocket Ebook
An older ebook format associated with Mobipocket and early Kindle publishing workflows.
About this format
MOBI is an older ebook format that became tied to early Kindle workflows. Modern Kindle publishing has moved toward newer formats, but MOBI files still appear in archives and personal libraries.
Use MOBI only when an older device or archive requires it. EPUB is usually the better open source format today.
Real-world samples & file sizes
MOBI samples should be judged in the sizes people actually receive, upload, or export. These reference cards show the common shapes and settings to check before choosing a conversion target.
international page
The default document shape for many countries.
US page
Important for North American documents.
report
Checks navigation, thumbnails, and file size scaling.
image-heavy file
Useful when the format often stores scanned pages.
Reference dimensions are platform-style targets. Compatibility and format facts are verified from the linked online sources below.
Pros
- +Works with some older Kindle-era libraries
- +Small ebook files
- +Common in legacy ebook collections
Cons
- −Legacy format
- −Weaker modern layout features than EPUB
- −Limited non-Kindle relevance
MOBI vs other formats
| vs | Size | Quality | Note |
|---|---|---|---|
| EPUB | Similar | EPUB is more modern | EPUB is the better authoring and interchange target. |
| Usually smaller | Reflowable text | PDF preserves pages; MOBI preserves reading flow. |
Where it works
- Reader app required
- Browsers do not open MOBI natively
- Calibre
- older Kindle apps/devices
- ebook converters
Frequently asked questions
- Should I publish a new ebook as MOBI?
- Usually no. EPUB is the better modern source format unless a specific workflow requires MOBI.
- Can I convert MOBI to EPUB?
- Often yes with ebook tools, but DRM-protected files cannot be freely converted.
Sources
- Library of Congress - Mobipocket - MOBI format description and history
- Library of Congress file format descriptions - archival format descriptions and sustainability notes