The short version
- A ligature is one drawn shape that stands in for two or more letters, like a joined th or ff, so the pair looks the way you actually write it.
- Fonts trigger them automatically through a rule table inside the file. Type t then h, and the app swaps in the joined shape.
- For cursive, ligatures are what make words flow. For print handwriting, they rarely matter, because the letters do not touch anyway.
- SnapFont does not make ligatures. Calligraphr does, on its Pro plan. Whether you need them depends on how you write.
What a ligature actually is
When you handwrite the word the, your pen probably does not lift between the t and the h. The crossbar of the t runs straight into the h, and the two letters share ink. A font that has one shape for t and one for h cannot draw that; it puts the two next to each other and they either touch awkwardly or not at all.
A ligature fixes that by giving the font a third shape: the joined thas one outline. Inside the font file there is a rule that says "when t is followed by h, use this shape instead." You type two letters; the app draws one glyph. You never see the swap happen.
Typography has used these for centuries. The classic ones are fi, fl, and ff, where the top of the f would otherwise crash into the next letter.
How the font knows when to use one
The font file carries a table of substitution rules (typographers call this the GSUB table). Each rule is a pattern and a replacement. The app doing the typing checks each pair of letters against the rules and swaps where it finds a match. This is why ligatures work in Word and Pages and Procreate without any setting: it is a property of the file, not the app.
Some apps let you turn them off, and a few older ones ignore the table entirely, so a font that depends on ligatures for its look will fall apart in those.
Do you need them for a handwriting font?
It depends entirely on whether your letters touch when you write.
- Cursive or joined writing. Yes, and a lot of them. Without ligatures a cursive font reads as a row of disconnected loops, which looks worse than a print font. This is the case where a tool with ligature support earns its price.
- Print handwriting, letters separate. No. Each letter stands alone on the page already, so the font drawing them one at a time is accurate. The only pairs worth considering are the ones where your writing genuinely overlaps, and most people have one or two at most.
- Somewhere between. Most people. A handful of pairs you always join and the rest separate. A print font with tightened spacing usually gets close enough that nobody notices.
Which tools do it
Calligraphr supports ligatures on its Pro plan: you write the joined pair in its own template cell and the tool builds the rule. Desktop editors like FontForge and Glyphs let you define any substitution you want, with a learning curve to match. SnapFont does not do ligatures; it builds a print font from 72 single letters, sizes and spaces them from your sheet, and stops there. That is the right trade for most people and the wrong one for a cursive writer. The full comparison is in SnapFont vs Calligraphr.
A cheap substitute for the common case
If you only have one or two pairs that bother you, reduce the letter spacing in whatever app you are typing in until those pairs overlap the way they do on paper. It is not a ligature, the shapes do not merge, but at reading size the eye stops noticing. That trick covers more cases than people expect.