MOBI is now a legacy format because Amazon discontinued support for it in 2023. You can still convert PDF files to MOBI using online tools or desktop software, but for modern Kindle devices, it’s better to use AZW3 or EPUB instead.
The MOBI format has officially entered legacy status, but even without Amazon’s support, many readers continue to use it. Whether you use an older Kindle model or need to maintain long-standing eBook collections, PDF to MOBI conversion can still be helpful.
In this guide, we’ll show you the easiest ways to convert PDF to MOBI, explain when it still makes sense to use this file format, and highlight modern alternatives that work better with today’s Kindle devices.
What is a MOBI file?
MOBI is an eBook format originally developed by Mobipocket and later acquired by Amazon. It was designed specifically for Amazon Kindle devices and apps.
With MOBI, you can use bookmarks, add notes, and sync your reading progress across Kindle devices. This format uses reflowable text, so readers can adjust font sizes and layouts to read comfortably on any screen.
Current status: Since December 20, 2023, Amazon's Send to Kindle feature no longer supports MOBI files. This means you can no longer send MOBI files to Kindle devices or apps through email, the Send to Kindle app, or the web interface. Existing MOBI files on your device still work, and you can still transfer new MOBI files by USB. This shift reflects Amazon's move toward more advanced formats like EPUB and AZW3.
What formats does Kindle support?
Kindle devices and apps support various file types, which generally fall into two categories: proprietary Kindle formats and universal formats.
Proprietary Kindle formats
Amazon has developed several file types specifically for Kindle devices:
AZW3 (KF8): The modern Kindle format that replaced MOBI, offering better typography, layout improvements, and stronger support for complex formatting.
AZW: Amazon's original proprietary format, similar to MOBI but with additional DRM (Digital Rights Management) to prevent unauthorized copying.
KFX: The newest Kindle format that offers improved typography, hyphenation, and high-quality page layout.
MOBI: A legacy format.
These proprietary formats offer the best reading experience on Kindle devices, with full support for features like Whispersync (syncs your reading progress), X-Ray (lets you explore characters and key terms), and Word Wise (shows quick definitions for challenging words).
Universal formats
Kindle also supports standard eBook and document formats:
EPUB: The industry-standard eBook format. Kindle now accepts EPUB through Send to Kindle and automatically converts it to AZW3 or KFX.
PDF: Supported but not optimized for e-readers due to fixed layouts.
TXT: Plain text files with no rich formatting, only basic structure.
HTML: Saved web pages.
DOC/DOCX: Microsoft Word documents.
Can Kindle read PDF files?
Yes, Kindle devices can read PDF files, but the experience isn't optimal. PDFs use fixed layouts designed for specific page sizes, which doesn't translate well to e-reader screens. Text doesn't reflow, meaning you often need to zoom and pan to read comfortably. Font sizes can't be adjusted easily, and the reading experience lacks the fluidity you'd get with native Kindle formats.
PDFs work relatively better on larger Kindles like the Scribe or Oasis, where the screen size more closely matches standard document dimensions. On smaller Kindles, PDF files are hard to read without constant zooming.
How to read PDF on Kindle
You can read PDF files on a Kindle in two ways: send the PDF to Kindle as it is or convert it to a format that’s easier to read on an e-reader.
Send to Kindle: Amazon’s Send to Kindle service lets you email a PDF directly to your device using your Kindle ’s unique address or the Send to Kindle app. It keeps the original PDF layout intact, but it won’t fix the readability issues that PDFs often have on smaller screens.
Convert to Kindle-friendly formats: For a better reading experience, convert PDF to a format that is optimized for e-readers. You can let Amazon convert the PDF when using Send to Kindle, or use third‑party tools for more control over the output. Consider some of our conversion tools:
How to convert PDF to MOBI
You can convert a PDF file to MOBI using either online converters or desktop software. Online tools are faster and more convenient, while desktop applications provide more control over the process.
Option 1. Use an online PDF to MOBI converter
Online Kindle converter tools offer the fastest way to create a MOBI file from PDF, with no software to install and no technical knowledge required.
How to convert PDF to MOBI online with PDF Guru
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Go to the PDF to MOBI conversion tool.
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The tool processes your file in about 10–30 seconds, depending on your file size and internet connection.
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Download the converted MOBI file to your device. PDF Guru also saves a copy to your account for easy access later.
If you ever need the reverse conversion, use the MOBI to PDF tool and follow the same steps.
Option 2. Convert PDF to MOBI using Calibre
Calibre is open-source eBook management software available for Windows, Mac, and Linux. While the interface has a learning curve, it offers extensive customization options for power users. You can adjust everything from metadata and cover images to layout, making Calibre a great choice if you want precise control over your eBook formatting.
How to convert PDF to MOBI with Calibre
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Download and install Calibre.
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Launch Calibre and click Add books to import your PDF file.
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Select the PDF in your library.
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Click Convert books in the toolbar.
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In the conversion window, select MOBI as the output format from the dropdown menu.
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Adjust other settings if you want (page setup, fonts, table of contents).
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Click OK to start the conversion process.
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When finished, right-click the book and select Open book folder to find your file in MOBI format.
How long does Calibre take to convert PDF to MOBI?
Calibre’s conversion speed depends on the size of your PDF, how complex its layout is, and your computer's processing power. Simple text-based PDFs convert in seconds, while more complex files can take several minutes. On most computers, a typical 200-page eBook converts in under a minute.
MOBI vs. PDF: What is better for a Kindle eBook?
When choosing between MOBI and PDF for your Kindle, consider which factors matter most to you. Here's how these formats compare:
| Criteria | MOBI | |
|---|---|---|
| Support status | Fully supported across all Kindle devices and apps | Legacy format; Amazon stopped accepting new MOBI files in 2023 but existing files still work |
| Compatibility | Works on virtually any device but isn't optimized for e-readers | Originally designed for Kindle devices but now replaced by AZW3, KFX, and EPUB |
| Text reflow | Fixed layout; text doesn't adjust to screen size | Reflowable text adapts to any screen size and allows font customization |
| File size | Larger due to embedded images and fixed layouts; can impact e-reader performance | Generally smaller and more lightweight, optimized for mobile reading |
| Image handling | Excellent image quality and layout accuracy | Limited image support; graphics may not display as well |
| Reading features | Basic bookmarks and annotations | Supports bookmarks, notes, and syncs your reading progress with other Kindles |
| Printing | Ideal for print; preserves exact layout and formatting | Not intended for print; formatting may appear off on paper |
Bottom line: PDF is the better choice when you need to preserve exact layouts, high-quality images, or plan to print documents. MOBI was historically better for reading on Kindle devices than PDF because of reflowable text and smaller file sizes, but in 2025 it is a legacy option and no longer the best choice. If you have a newer Kindle, formats like AZW3 or EPUB offer better features, compatibility, and ongoing support.
For more details on choosing between eBook formats, check out our EPUB vs. MOBI comparison guide.
Tips to convert PDF to MOBI without losing formatting
If you want to convert PDF to MOBI for Kindle, you need to take a few extra steps to protect its layout and formatting. If you follow these tips, you'll have more control over how your converted file looks and how readable it is on your device.
Use reliable online tools. For simple conversions, tools like PDF Guru work quickly and handle most standard PDFs well with no installation required. Before choosing an online converter, check reviews and user feedback on platforms like Trustpilot.
Simplify complex PDFs. PDFs with multi-column layouts, nested tables, or heavy graphics often convert poorly. Before converting, edit PDF files to remove or simplify these elements. Even small adjustments can dramatically improve the final result.
Try converting PDF to EPUB first. Converting your PDF to EPUB before generating a MOBI file can preserve more formatting. If you still need a MOBI file afterward, you can convert the EPUB, but keep in mind that modern Kindles still turn EPUB files into a Kindle format during transfer.
Optimize image quality. High-resolution images can inflate file size and cause display issues on e-readers. Before converting, reduce images to around 300 DPI or lower.
Boost your productivity with PDF Guru
PDF Guru lets you turn PDF into MOBI in seconds, with clean formatting and no software to install. Whether you’re updating an older Kindle library or preparing files for a legacy device, our platform gives you a fast, reliable way to create MOBI files whenever you need them.
