I am testing some of the Google free fonts for embedding in epub files (following directions from this article):

The downloadable fonts are TTF, but the epub 3 spec says:

Reading Systems with a CSS Viewport must support OpenType [OpenType] and WOFF [WOFF] fonts embedded using the @font-face rule.

This suggests that OTF is better/more reliable, but this article --written by a fairly informed individual -- is recommending TTF (especially for Kindles).

So my question is: 1)does converting ttf to otf create bloat or artefacts which might justify just including the TTFs without converting them? and 2)Has anyone noticed different levels of support for TTF or OTF in various reading systems?


  • According to Wikipedia, OpenType is a successor format to TrueType, and .otf and .ttf are both accepted file formats of the OpenType standard; thus, reccomending to use an OpenType font doesn't necessarily means to use a specific file format.
    – Sekhemty
    Apr 26 '17 at 15:11
  • Thanks, this is actually news to me. I thought OpenType was equivalent to OTF! Apr 27 '17 at 16:55
  • It was news even to me, I learned it while gathering info. Anyway I haven't read the whole epub specification, so you might want to double check if the two formats are considered interchangeable in this context.
    – Sekhemty
    Apr 27 '17 at 17:40

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