As avid eBook readers and library managers ourselves, we've tested dozens of converters to help you navigate the confusing world of eBook formats. With over a dozen common file types—each optimized for specific devices and features—you'll often need a reliable converter to make your books compatible.
In this expert guide, we break down everything you need to know about eBook conversion, drawing from years of hands-on experience with popular readers like Kindle and beyond.
eBook converters fall into two main categories: web-based tools and standalone desktop apps. We've evaluated both for reliability, format support, and ease of use.
The top free desktop tool is Calibre, a powerhouse we've relied on for over a decade to manage vast eBook libraries.
If you're serious about eBooks, Calibre is likely already on your system. Beyond conversion, it excels at metadata editing, cover art management, and wireless device syncing.
Calibre supports inputs like EPUB, AZW, MOBI, LRF, ODT, PDF, CBZ, CBR, CBC, CHM, FB2, HTML, LIT, PRC, PDB, PML, RB, RTF, SNB, TCR, and TXT. Outputs include EPUB, MOBI, AZW3, AZW, PDB, FB2, OEB, LIT, LRF, PML, RB, PDF, SNB, and TXT.
Another solid free choice is Any eBook Converter. It handles EPUB, MOBI, AZW, PDF, and TXT, with built-in metadata editing and automatic DRM removal. For DRM details, see our in-depth guide: How To Remove DRM From Every Ebook You Own. Nobody likes DRM. We all understand why it exists, but that doesn't mean we're ready to accept it. Therefore, this article explains how to remove DRM from every ebook you own.
Auto Kindle eBook Converter is another Windows freebie, ideal for turning PDF, LIT, and HTML into Kindle-friendly MOBI.
Most other desktop apps require payment, so if those don't fit, turn to web options below.
Free online converters abound, but quality varies. From our extensive testing, these five stand out for all formats: 5 High Quality Online eBook Converters for each format. Ebooks with their multiple formats can be confusing. These online flawless ebook converters will serve all your needs.
Choosing the right format depends on your device. The most common are EPUB, MOBI, AZW, and PDF.
EPUB is the open-standard leader—free, versatile, and widely supported, though publishers may add (removable) DRM.
MOBI, a 2001 Mobipocket creation acquired by Amazon in 2005, lacks audio/video support unlike EPUB.
AZW (and AZW3) is Amazon's proprietary MOBI-based format; Kindle exclusives ship in AZW, but third-party readers often can't open it.
PDFs work on most readers but frequently suffer reflow and layout issues.
Other formats include CBR/CBZ for comics, RTF (enhanced TXT), Apple's IBA, and DJVU. For full breakdowns, check The different eBook formats explained: EPUB, MOBI, AZW, IBA and more. In this article we take a look at all the common eBook formats, explain their pros and cons, and tell you which eBook readers support them.
Amazon has sold over 100 million Kindles since 2007, dominating the market. Yet, with a huge library from diverse sources, their limited formats can frustrate.
No native EPUB, CBR/CBZ, DJVU, or FB2 support. Kindles handle only AZW, AZW3, DOC, HTML, MOBI, PDF, and TXT—necessitating conversions for many files.
Calibre and Any eBook Converter convert EPUB to AZW/AZW3, but we recommend MOBI for broader compatibility across Kindles and other readers.
In Calibre, set auto-conversion: Preferences > Interface > Behaviour, choose MOBI as preferred output.
Then, Preferences > Adding books > Adding Actions tab: enable Automatically convert added books to current output format. Apply changes.
For existing books, select them, click Convert books > Convert individually or bulk, set output to MOBI, and OK.
Learn more in our Calibre guide: How to convert ebooks to Kindle format when importing into your library. Caliber has another nifty trick up its sleeve: it can automatically convert any ebook to Kindle MOBI format when you import it into your library.
PDFs shine for desktop viewing. For quick conversions, web apps are ideal.
With Online-Convert, select Convert to PDF under eBook Converter, click Go. Upload via Select Files, tweak title, layout, metadata, then Start Conversion.
PDF to EPUB, MOBI to AZW, or any combo follows similar steps with these tools.
Need free eBooks to convert? Explore our picks: The 7 Best Free eBook Download Sites. ¿Por qué gastar dinero comprando libros electrónicos cuando puede descargar libros electrónicos gratuitos en su lugar? Aquí hay algunos sitios ingeniosos donde puedes hacer eso.
