Free monospace fonts

A monospace font gives every character the same width, which is the whole point and also the whole constraint. It is what makes a column of numbers line up and a block of code hold its shape, and it is why an m has to be squeezed and an i has to be padded out with serifs until it fills its slot. Every design decision in this category is downstream of that one rule.

For code, the thing that matters most is not beauty but the characters you would rather not confuse: the zero against a capital O, the lowercase l against a capital I against the digit 1. Faces built for programming solve this deliberately — a slashed or dotted zero, a tailed l, a serifed I. Faces built for typography rather than code often do not, and you find out at two in the morning.

The second decision is whether you want ligatures. Some of these families draw an arrow when you type a hyphen and a greater-than sign, and a not-equals sign when you type an exclamation mark and an equals. Programmers are split on it and both sides are reasonable; it is a setting in your editor, so the font is not the commitment it looks like.

Outside code, a monospace face is a strong editorial choice rather than a neutral one. It reads as technical, as documentary, as unfinished on purpose. That is useful in captions, tables, tickets and interfaces where numbers change, and it is tiring in a paragraph — the even spacing that keeps a column honest is the same thing that makes a sentence feel like it is being typed rather than read.