What is .mobi?
.mobi (Mobipocket) is an e-book format originally created by Mobipocket and later used by Amazon Kindle as a core part of its ebook ecosystem. It is a binary container format optimized for small devices and limited bandwidth, storing reflowable text, basic formatting, and embedded images.
This quick guide explains when to use .mobi files, how to open them on any device, and how to share them instantly with FileXhost.
When to use .mobi files
- You have an existing library of older Kindle or Mobipocket e-books.
- You are distributing e-books specifically for legacy Kindle devices that prefer MOBI.
- You need a compact, reflowable e-book format that works on many older e-readers.
- You plan to convert existing MOBI books into newer formats like EPUB or AZW3.
How to open .mobi files
MOBI files are primarily associated with Amazon Kindle devices and apps. You can open .mobi files by transferring them to a Kindle e-reader, using the Kindle desktop/mobile apps (where supported), or importing them into library managers like Calibre. Many modern reading apps focus on EPUB instead, so conversion may be required. You can upload .mobi files to FileXhost to host and share them as downloadable e-book files.
Algorithm details
The MOBI format is based on the older PalmDOC and Mobipocket standards. Internally, it uses a binary structure with records that contain text, images, and metadata. Text is typically compressed using a variant of LZ77 or Huffman-based schemes, and formatting is expressed through a restricted subset of markup. Kindle-specific variants extend MOBI with additional metadata and DRM layers.
Browser & platform support
- Desktop: Not natively supported by browsers; MOBI files are downloaded rather than rendered. Viewing usually requires Kindle apps or conversion to EPUB/PDF.
- Mobile: Readable via the Kindle app on iOS and Android or third-party readers that still support MOBI.
- OS: Supported on all major operating systems through Kindle software or Calibre and similar tools.
Format comparison
| Feature | Details |
|---|---|
| Modern Alternatives | EPUB and AZW3 are now preferred for most new e-books, offering richer formatting and better tool support. |
| Compatibility | Historically strong on Kindle devices, but less universal than EPUB across non-Kindle readers. |
| Layout | Reflowable text optimized for small screens, but with more limited styling compared to modern EPUB. |
| Longevity | A legacy format: still usable, but many publishers and platforms have moved away from MOBI. |
How to create mobi files
- Calibre: Convert from EPUB, DOCX, or other formats to MOBI for Kindle.
- KindleGen/Kindle Create (legacy tools): Previously used to generate MOBI or Kindle-ready files from source documents.
- Older Publishing Workflows: Some distributors still generate MOBI for backward compatibility.
- Online Converters: Web-based tools that turn DOCX, EPUB, or PDF into MOBI.
How to convert mobi files
- FileXhost: Upload .mobi files to host them as downloadable e-books for readers.
- Calibre: Convert MOBI to EPUB, AZW3, or PDF for better compatibility with modern apps.
- Online Tools: Services like CloudConvert or Zamzar that convert between MOBI and other e-book formats.
- CLI + Scripts: Use Calibre's command-line tools or Pandoc (via intermediate formats) in automated pipelines.
Advantages & disadvantages
Advantages
- Optimized for legacy Kindle devices and low-bandwidth environments
- Supports reflowable text and embedded images
- Widely used historically, so many older e-books are available in MOBI
Disadvantages
- Legacy format with declining support compared to EPUB and AZW3
- Limited styling and layout capabilities versus modern e-book standards
- Often requires conversion to work well with non-Kindle readers
Tools & software
Readers
Amazon Kindle devices, Kindle desktop/mobile apps (where supported)
Managers
Calibre, BookFusion, other e-book library tools
Converters
Calibre, CloudConvert, Zamzar, Kindle Previewer (legacy)
Frequently asked questions
Is MOBI still used for new e-books?
MOBI is largely considered a legacy format. Most new e-books are published as EPUB, with Kindle-specific formats like AZW3 or KFX used internally by Amazon. MOBI remains relevant mainly for older devices and backlist catalogs.
Should I convert MOBI to EPUB?
Yes, if you want the broadest compatibility across non-Kindle devices and apps, converting to EPUB is recommended. Tools like Calibre can batch-convert MOBI to EPUB and preserve most formatting and metadata.
Can I read MOBI files without a Kindle?
Yes. You can use Calibre on desktop, some third-party mobile readers that still support MOBI, or convert MOBI to EPUB or PDF for use in your preferred reading app.
Does MOBI support DRM?
The MOBI format itself can be wrapped with DRM when distributed through platforms like Amazon. DRM-free MOBI files can be converted and moved freely, while DRM-protected files may be locked to specific apps or devices.
Technical specs
- File type
- Ebook
- Extension
- .mobi
- MIME type
- application/x-mobipocket-ebook
- Compression
- Lossless
- Max file size on FileXhost
- Up to 25 MB per file on the free plan and up to 1 GB on Pro FileXhost accounts.
Share .mobi files instantly
Upload your .mobi file to FileXhost to get a clean, shareable URL in seconds. View the file in a modern browser, protect access with optional settings, and let others download it without any confusing ads or cluttered file pages.
Upload .mobi file