What Is a Ligature in Typography? fi, fl and Beyond

A ligature is one glyph that stands in for two or more letters. The classic cases are fi, fl, ff, ffi and ffl. In a typeface where the top of the f reaches far to the right, it would crash into the dot of the i. A ligature solves the crash by drawing the pair as one shape, in which the hook of the f absorbs the dot or merges with the l.

The word comes from Latin ligare, “to bind”. Medieval scribes bound letters together to save time and space, and early printers copied those habits with special sorts, so a good deal of ligatures are inherited from handwriting.

Standard and discretionary ligatures

Most modern fonts include ligatures in two groups, switched on by OpenType features:

Feature	Tag	Purpose	Example
Standard ligatures	`liga`	Fix collisions, on by default	fi, fl, ff, ffi
Discretionary ligatures	`dlig`	Decorative, off by default	st, ct in old-style fonts
Contextual alternates	`calt`	Swap shapes depending on neighbours	Connected script letters

The text you type does not change. The font looks at the sequence f then i and swaps in the ligature glyph for display. If you copy the text, you copy fi, as typed. That is why selecting half of a ligature in a PDF or web page can look odd, but the text itself is still two letters.

Letters that began as ligatures

Some familiar characters have evolved from ligatures into letters in their own right. The ampersand & is a ligature of e and t, from Latin et. The German ß (eszett) comes from a long-s and z or s combination. æ and œ began as ae and oe. These now have their own code points and are treated as separate letters or symbols in their languages.

Unicode presentation forms

Unicode encodes a few Latin ligatures as characters in the Alphabetic Presentation Forms block: ﬀ (U+FB00), ﬁ (U+FB01), ﬂ (U+FB02), ﬃ (U+FB03), ﬄ (U+FB04), and ﬅ and ﬆ for long-s t and st. They exist for round-tripping legacy encodings, and Unicode discourages using them in new text. Searching for “file” will not find “ﬁle” unless the software applies compatibility normalisation (NFKC), which maps ﬁ back to fi.

Ligatures in Arabic and Indic scripts are different: these are essential, since the connected letters have no separate forms in many contexts.

Ligatures in lettering and handwriting

In hand lettering and script, you create ligatures by design: letting the crossbar of a t run into the next t, joining o to r with a continuous stroke, or tucking a dot into an f hook. Cursive handwriting is full of joins, and some pairs, like th or ft, are written with a single continuous movement, as covered in cursive joins. A calligrapher chooses where to ligate, as part of a word’s rhythm, as part of what a script font mimics with contextual alternates.

Ligatures in fancy Unicode text

Fancy text generators do not create ligatures; they swap each letter for a separate character. If you type “fi” in the bold text generator, you get two bold characters, and no ligature forms between them. A few characters, such as ﬁ, can be pasted in, but they will look similar to plain “fi” in many fonts and cause search and accessibility problems. Our Unicode explainer describes why styles replace characters instead of formatting them.

Common confusions

A ligature is not kerning. Kerning moves two separate glyphs; a ligature replaces them with one glyph.
Ligature is not always decorative. Standard ones fix collisions.
The medical meaning of ligature (a surgical tie) is unrelated except for the shared Latin root.

Frequently asked questions

Why do fi and fl need a ligature?

In many fonts the hook of the lowercase f reaches over to where the dot of the i or the ascender of the l sits, so the letters collide or leave an awkward gap. A ligature redraws the pair as one shape in which the f hook merges with the dot or ascender, so the two letters read cleanly.

What is the difference between a ligature and a digraph?

A ligature is a typographic shape that joins letters, while the letters stay separate in meaning. A digraph is a pair of letters representing one sound, such as sh. Some pairs are both: the letter æ began as a ligature of a and e and is now an independent letter in several languages.

Should I copy the ﬁ character into text?

Usually not. The Unicode presentation form ﬁ (U+FB01) is meant for compatibility with old encodings, and search, spell checkers and screen readers may not treat it as the letters f and i. Type fi normally and let the font apply the ligature itself when it supports one.

Are programming ligatures the same thing?

Same mechanism, different goal. Coding fonts such as Fira Code use contextual substitution to draw sequences such as != or => as single connected symbols. The underlying characters stay as typed, so the text remains searchable and copy-pasteable. Many editors let you switch them off.