If you just create a one-time greeting card or invitation with a free front from the internet, font quality might not be you biggest concern. What you see is what you get. You set the text you need and if it looks good to you, your job is done. But for bigger projects and design work for clients, you will need to make sure the chosen fonts have a decent quality and will not cause problems in the future. Here are some guidelines to judge the quality of a font. 

No missing characters

As discussed in the lesson “The character set”, make sure the font contains a complete base character set and all scripts and special characters necessary for the intended use.

Free fonts often do not even cover a basic character set

Consistent strokes

Handwriting is a series of strokes and the outline of the letters is a result of the writing tool. But the common digital font formats do not actually “write” a text like a calligrapher would. Instead, the fonts contain vector outlines, which just give the appearance of a writing tool. It depends on the skill of the type designer how convincing that looks. Inexperienced type designers often struggle to create consistent curved strokes, since what they have to work with are the outlines of the letters. As a result, the individual letters might appear unbalanced and even the entire page might look uneven, which can diminish the reading comfort. 

A free font from dafont.com with inconsistent strokes

Spacing: sidebearings and kerning

The white space between the letters is usually just as important as the letterforms itself. A type designers tries to balance those areas of white space to create a consistent pattern of stems and white space. Each character has a setting for the space on the left and on the right side of the visible letterforms. Those values are called sidebearings. For some letter pairs, using these default spacing values is not enough, so an exception can be added. This is called kerning. If you type LAWYER for example, the A and W can and usually should be moved closed together through a kerning pair for A and W. Reducing the white space makes sure that the word is still easily understood as such and the reader isn’t tempted to see a space character there. 

Inconsistent whitespace can significantly decrease the legibility and the reading comfort. Especially for longer texts, fonts need spacing with a sufficient quality. Try to set entire paragraphs and check the consistency of the letter spacing. It can also help to print out a text to judge it on paper.

The default spacing between the letters is rather uneven in the first line (Tiresias Infofont) and well done in the second line (Myriad) 

You can also check if the font has typical kerning pairs. Kerning usually needs to be applied to characters which create a lot of white space around the letterform, like A, Y, W, L, T, P or an f with a long arc. Keep in mind that kerning often brings letters close together to avoid too much white space, but it might also be applied to avoid unwanted collisions, which could decrease the legibility. For example: what happens when an f is followed by a character with an ascender (like k or l), a bracket or a quotation mark?

The first font doesn’t deal properly with letter combinations such as VA, Ta and fe. 

Outline anchor points

A letter in a digital font consists of a mathematical description of an outline. The outline consists of anchor points, connected through lines or curves. A quality font uses exactly the right amount of anchor points at the right positions. Fonts with insufficient quality might have have unwanted dents and bulges. In addition, too many anchor points (which are often the result of auto-tracing) can become a serious problem. It can slow down the design software or even cause errors when the text is displayed, printed or for example cut in vinyl for a sign. 

Overshoot and screen optimization

Letterforms can be understood as a combination of basic geometric shapes like rectangles, triangles and circles. When used next to each other, those shapes need a visual correction to give the appearance of the same visual height. Some shapes need to be extended over the base line, the x-height or the capital height in a font. Type designers call this overshoot and setting it correctly requires some experience. Inexperienced type designers might not set this correctly or maybe don’t consider it at all. 

Not a bug, it’s a feature! Different character shapes require different heights to create visually even letter heights.

It gets even more tricky when the vector outlines are shown on a screen. In this case, the letterforms are forced into a grid of pixels and the goal is to maintain the letterforms as best as possible using consistent strokes. Type designers can influence this not only through their letter design, but also through the process of font hinting, which gives the render engine instructions or “hints” about how to deal with the outlines in a small pixel grid. If the font you consider needs to work in small sizes on screens, you should test the render quality on different devices and in different applications. Do all the letters remain legible? Are there gaps in the letterforms, e.g. because hairlines in the font aren’t rendered at all? Do the horizontal lines—like the base line and the x-height—appear visually flat or are parts of the letters forced under or over those lines for some letters but not others? This would be a typical result of missing or insufficient hinting. 

Even in a small pixel grid, the stroke width and the sizes of the letters should appear consistent.

Use trustworthy sources

There is no simple correlation between the price of a font and its quality, but as you can imagine, the quality of fonts varies from type designer to type designer or from type foundry to type foundry. Try to learn which sources you can trust and which to avoid. If you intend to work with fonts a lot in the future, you should get familiar with the designers and foundries in the type business. How much experience does a type designer have? Did they study type design? How much experience do they have with the supported scripts of a font or alternatively, did they work with experts of that particular script? And so on. The more you know, the easier it gets to make an informed decision about the expected quality of a font.