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Evaluating typefaces for electronic reading

On various devices that use eInk, it is possible to add your own font files, so that you can read using your favorite typeface at your desired size and thickness. Depending on the device you are reading on, you may find that some fonts work better than others.

You might be wondering why that is. Sometimes, fonts won’t be displayed correctly. Especially on platforms that use different rendering engines, this can be a real issue.

To properly evaluate whether a typeface works, it is imperative to evaluate the correct font files with correct metadata, otherwise the fonts in question may not load correctly, or may be displayed incorrectly.

A typeface is a family of fonts, often using different weights and appearances. An individual font file, often ending in .otf (for OpenType fonts) or .ttf (for TrueType fonts) usually encompasses only a single style.

Variable fonts also exist, and those can be scaled in various ways (thickness, width, etc.), depending on how the typeface was designed in the first place. Most regular variable fonts only scale in terms of weight, and a family often includes two files: one regular variant, and one italic variant.

Unfortunately, variable fonts are not widely supported at this point in time on e-readers. In particular, Kindle and Kobo devices do not properly support these font files as of 2025.

Sourcing fonts

It is important to

Copying font files

For e-readers, it is advisable to copy at least four different styles: Regular, Italic, Bold and Bold + Italic (often suffixed as BoldItalic).

The collection of fonts that I have curated for Kobo devices has those files named correctly. For example, NV Garamond, which is simply an altered version of the excellent EB Garamond, will have the following files that will need to be transferred:

- NV-Garamond-Regular.ttf
- NV-Garamond-Italic.ttf
- NV-Garamond-Bold.ttf
- NV-Garamond-BoldItalic.ttf

Often, it is sufficient to copy these files over to the fonts directory on your e-reader. For concrete instructions, please consult the manual of your particular device.

There is one other thing you should take into consideration: in order to avoid issues, you should always restart your e-reader when side-loading fonts.

This may require you to hold down the power button for an extended period of time before the device will restart. Again, consult the manual for your device in order to find out how to properly restart your e-reader.

A chapter intended for font testing

This is a paragraph, which should contain enough text for you to be able to decide what font size and weight is your preference. Another thing you may want to adjust is the distance between different lines of text, this is called line spacing. Depending on the built-in metrics of the font, line spacing may vary significantly.

For fonts included in my curated collection, line height has been adjusted with the font-line program and set to 20%. This makes the spacing a little bit more consistent between different typefaces. You may be able to further alter the font weight, for example on Kobo devices.

Another important thing is to make sure that each of the four core fonts are being displayed correctly, i.e. no style mixing occurs. If font metadata is set incorrectly, you may find that all text is being displayed in bold or italicized (or worse, both).

If the font is not being displayed correctly here, it is very likely that it will not be displayed correctly in other books on your device. You may wish to pick a different font or reach out to the creator of the typeface for a potential fix. Alternatively, you may wish to fix the metadata yourself.

Font style test

As part of the next paragraph you can find four sentences, each of which corresponds to a different font file. You can use this section as a sort of test.

REGULAR
This sentence should be displayed normally.

ITALIC
This sentence should be displayed using italics.

BOLD
This sentence should be displayed in bold.

BOLD ITALIC
This sentence should be displayed in bold, and should be italicized.

If the paragraphs above are all distinct and rendered correctly, you can assume that the typeface is being rendered correctly and you can enjoy your reading adventures without issues.

It is, of course, always possible that books provided by a third party or sold to you contains problematic markup, which may also cause rendering issues. In that case, you may wish to contact support for a potential fix or refund.