When you cre­ate doc­u­men­ta­tion for tablets or smart­phones, should you cre­ate an EPUB file or an HTML5 file?  As usu­al, it depends on your audience.

What is an EPUB file and how does it differ from HTML5?

An EPUB doc­u­ment is an XML file that is zipped file with the .epub exten­sion. You cre­ate EPUB files using Microsoft Word, Adobe InDe­sign, and help author­ing tools such as Mad­Cap Flare and Adobe Robo­Help. This enables users to read the file in Adobe Dig­i­tal Edi­tions, or iBooks, Apple’s free e‑reader for iOS.

HTML5 is not soft­ware that has to be installed but rather a new ver­sion of HTML that appears in your brows­er. It’s a work in progress. Safari and Chrome pro­vide good sup­port for HTML5 where­as Inter­net Explor­er has been slow to sup­port it.

Why would you create an EPUB file?

The main advan­tage of an EPUB file is that is changes the flow of the text, based on the device you have. If your users are view­ing your con­tent on an iPhone, the pre­sen­ta­tion of the con­tent appears dif­fer­ent­ly than if it is viewed on a PC or an iPad. For exam­ple, see the fol­low­ing two screen shots:

With EPUB files, you can also choose the fixed lay­out option as well. Fixed lay­out EPUB files are per­fect for cook­books, illus­trat­ed books, and some text­books. With the fixed lay­out func­tion­al­i­ty you can embed fonts, choose par­tic­u­lar text sizes, and pre­cise­ly posi­tion images. Basi­cal­ly, fixed lay­out options give con­tent cre­ators greater con­trol over the pre­sen­ta­tion of a doc­u­ment. For the tech­ni­cal details of a fixed lay­out option for EPUB, see the Fixed Lay­out Doc­u­ment sec­tion of the Inter­na­tion­al Dig­i­tal Pub­lish­ing Forum web site.

One dis­ad­van­tage of an EPUB file is that it may require your users to install soft­ware such as iBooks, which is not pre-installed on iPads or iPhones.

Why would you create an HTML5 file?

You prob­a­bly want to con­sid­er cre­at­ing an HTML5 file when your users are run­ning browsers (such as Safari or Chrome) that sup­port it. If you are con­fi­dent that your users are using one of these browsers, it’s eas­i­er for them to view your work. There is no extra app to install.

Anoth­er advan­tage of HTML5 is that if your user assis­tance is avail­able in a brows­er, any revi­sions to the con­tent will imme­di­ate­ly be seen by your users. With an EPUB file, there’s the addi­tion­al work of cre­at­ing the lat­est EPUB file and dis­trib­ut­ing it again to your users.

HTML5 also sup­ports offline support—meaning that you can view the con­tent when you have an Inter­net con­nec­tion, your brows­er caches the con­tent, and then you can view the same con­tent when you are offline. This may be per­fect for users who need user assis­tance but do not have a reli­able net­work connection.

Other Resources

* What is EPUB 3? by Matt Gar­rish ( a free O’Reil­ly book).

* Eliz­a­beth Castro’s book EPUB Straight to the Point. 

* Test your brows­er for HTML5 sup­port

*A free online book: Dive into HTML5 by Mark Pilgrim.