I imagine that the width of the space between words is set by a font specifics. Somewhere in there it states how big it should be.

Is the space width equal to some letter width or is this some custom number the font designer chooses?


It’s the width of the space character (U+0020), which can be controlled by the designer just like the width of any other character. This character does not even have to empty (example), though this won’t work in many renderers as they like to control spaces themselves (e.g., for justification).

Now, strictly speaking, a bit of the space between words comes from the letters themselves, which are not crammed on their virtual sort, but usually have a bit of free space to the left and right, which is called bearing. This bearing ensures that letters do not touch when composed within a word and allows to take into account the optical width of the letter (because you do not want to kern everything). It can even be negative, e.g., the letter f usually has a negative right bearing. To illustrate this, here is an example where the vertical lines indicate the actual boundaries between glyphs:

enter image description here

  • Thanks for stopping by. I used string "m m" and "m". I measured the width in px of "m m" and subtracted twice the width of "m" to gain the width of space. I then repeated this for different letters. I noticed there is small difference in space width-around 2%. Why is that? – sanjihan Sep 4 '17 at 6:19
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    Thanks for stopping by. – Don’t worry, I live here. As for the rest, please see my edit. – Wrzlprmft Sep 4 '17 at 8:57

When instructing beginners, I start them with exercises (rendering) using the lower-case "i" for word-spacing when using "close, but-not-touching" kerning practice. This "space" works for most display-sized headlines and for the bulk of situations.

I notice that this helps normalize the criticism that "professionals use spacing that is too tight and beginners to use spacing that is too loose."

  • I fail to see how this answers the question, which I understand to be about the implementation not about how to choose this width. – Wrzlprmft Sep 4 '17 at 8:32

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