Convert MOBI Online Free

About MOBI

Convert MOBI ebooks to and from the formats other software reads, in your browser. The work happens on your own device, so the book is never uploaded and you do not need a connection once the page has loaded.

What a MOBI file holds

MOBI started at a company called Mobipocket, who built it to make distributing digital books practical. Amazon bought them, and MOBI became the format the early Kindles ran on, which is how it ended up attached to an enormous library of ebooks. The useful property is reflowable text: the book re-lays itself to fit whatever screen and font size you are reading on, rather than being fixed to one page shape.

Open a MOBI file up and you find the Palm database architecture underneath, holding the text, the images and the metadata in a layout built for loading and displaying quickly on hardware that did not have much to spare. That structure is what lets the text reflow, so the same book works at whatever font size you prefer and whatever shape the screen is. Amazon's early Kindle ecosystem leaned on MOBI and the formats derived from it, AZW among them, which kept it central to digital reading until better formats arrived.

Strengths and limits

Text that reflows is the reason MOBI suited e-readers. Hold a Kindle in portrait or landscape, pick whatever type size your eyes want, and the book simply re-lays itself to fit. Fixed layouts cannot do that. It is why MOBI became the format the first Kindles ran on, and why so many existing ebook libraries are still full of it.

MOBI is a legacy format now. Amazon moved on to AZW3 and KFX, which do more, and it never had the open standardised status that EPUB has, so it stayed largely inside Amazon's world. The formatting is limited too, compared with what modern formats manage in styling, interactivity and embedded media.

MOBI Format Evolution

Mobipocket built MOBI in 2000, when the problem was that ebooks needed a format flexible enough for publishers to distribute and for a range of incompatible reading devices to open. It worked well enough that Amazon acquired Mobipocket in 2005 and put the format into the early Kindles. That is the moment MOBI stopped being one option among several and became what Kindle meant.

It picked up updates as it went, DRM support and better formatting among them. Then came AZW, a derivative of MOBI, which tightened Amazon's grip on how ebooks were distributed. New devices rarely use MOBI any more, but it has not gone away: a great many existing ebook libraries are still full of it, which is usually why anyone needs to convert one.

Choosing MOBI Format

Pick MOBI if you are aiming at Kindle devices, or if you are working through an older ebook collection that is mostly in it. It suits anything that wants reflowable text, which means novels and non-fiction rather than anything with a fixed layout. It is also the format some Kindle-oriented software expects, so choosing it can save a conversion step later.

Most people arrive here converting an EPUB or a PDF into MOBI, usually with Calibre or Kindle Previewer. Two things go wrong in that direction: embedded fonts and image scaling, both of which look fine until you open the book on the device. Going the other way, check the destination format actually supports what the MOBI is doing, because the fancier formatting often does not survive the trip. Either way, open the finished file on the real device before you trust it.

Working with MOBI files

You will encounter MOBI files in older Kindle libraries and ebook collections built around the early Kindle ecosystem.

To read one in a non-Kindle app, convert the MOBI to EPUB, which almost everything supports. If you want the current Kindle features, AZW3 or sending the file to your Kindle account is the better route, since Amazon is retiring MOBI.