Blog · Typography
Ligatures and dyslexia: are joined letterforms making text harder to read?
Most readers never notice ligatures. They are a quiet feature of quality typography - certain letter pairs like fi, fl, and ff are drawn as a single merged glyph rather than two separate characters. The result looks cleaner on paper. On screen, for some dyslexic readers, it creates a different problem: a letter that looked one way a moment ago now looks like something else entirely.
What a ligature actually is
Typographic ligatures date to the era of metal type. When a lowercase f was set next to a lowercase i, the curved terminal of the f physically collided with the dot of the i. Typographers solved this by casting the pair as a single piece of metal - one combined shape that avoided the clash and looked better on the page.
Digital fonts inherited the convention. In an OpenType font, the liga feature stores these pre-drawn combinations: most commonly fi, fl, ff, ffi, and ffl. When you type the word "find", many quality fonts will automatically substitute the fi pair with a single ligature glyph. You typed two characters; the font renders one shape.
If your browser is rendering a ligature-capable font, the left panel above should look slightly different from the right - the fi pair's dot may merge into the f's arm, and the two letters sit closer together as one unit. If both panels look identical, your current font does not use standard ligatures, or your browser has disabled them.
This is not an exotic edge case. Common web fonts including Georgia, Palatino, Garamond, and many of the polished sans-serifs available through Google Fonts include standard ligatures and enable them by default. In day-to-day web reading you encounter ligatures hundreds of times without realising it.
Why ligatures create problems for dyslexic readers
The core issue is letter-shape consistency. A dyslexic reader who has learned that the letter i has a dot above a vertical stroke may be confused when the same letter appears as part of an fi ligature, where the dot has merged into the connecting arm of the f or disappeared entirely. The letter looks different. The brain has to re-parse a shape it thought it knew.
For readers who are still consolidating their letter-recognition skills - children learning to read, or adults who read slowly precisely because letter-shape recognition demands conscious effort - this added variability is not trivial. Every time a familiar letter appears in an unfamiliar merged form, it introduces a small perceptual hiccup. String enough of those together across a long article and the reading effort increases noticeably.
The same research tradition that explains why b/d/p/q reversals are so persistent for dyslexic readers applies here. Dyslexia is, in significant part, a difficulty with the phonological and orthographic representations that connect a letter's visual form to its sound. Ligatures quietly add another layer of visual variability on top of an already effortful decoding process.
There is no large-scale peer-reviewed study specifically isolating ligatures as a variable in dyslexic reading comprehension - the field has generally focused on font choice, spacing, and weight rather than OpenType features. But the mechanism is well-grounded in what we know about letter confusability, and the practical complaints from dyslexic readers and teachers of dyslexic students are consistent: removing ligatures is a small change that sometimes produces a noticeable improvement in reading ease. It costs nothing to try.
Which ligatures cause the most trouble
Not all ligatures are equally problematic. The standard five - fi, fl, ff, ffi, ffl - vary in how much they distort the component letters.
The fi ligature is the most commonly cited offender. In most implementations, the dot of the i is absorbed into the crossbar or terminal of the f. A reader who identifies the letter i partly by its dot may misread the ligature entirely, or simply hesitate long enough to lose their place in the sentence. Words like "file", "find", "film", "first", "finish", and "figure" - all extremely common in everyday text - all begin with this pair.
The fl ligature tends to be less disruptive because the l has no distinctive feature that is absorbed. The letters flow together but remain roughly recognisable.
The double-letter ligatures ff, ffi, and ffl are rarer in everyday text but present in words like "effect", "office", "coffee", "difficult", and "official" - none of which are obscure. In an ff ligature, the two fs share a crossbar, which can make the pair look like an unfamiliar combined shape rather than two instances of a known letter.
Some OpenType fonts also include contextual alternates (calt) and discretionary ligatures (dlig) beyond the standard five. These include things like ct, st, and even whole-word ligatures in display fonts. Discretionary ligatures are almost never on by default in body text, but if you are using a premium or designer typeface, it is worth checking.
How to check whether a website is using ligatures
Open your browser's developer tools (right-click anywhere, choose "Inspect"). Select any paragraph of text. In the Computed Styles panel, look for font-feature-settings and font-variant-ligatures. If you see normal, common-ligatures, or no mention of ligatures at all, the browser is probably applying the font's default ligature behaviour - which for most quality fonts means ligatures are on.
You can also simply look at the word "difficult" in the page's body font. If the two fs share a crossbar, ligatures are active.
How to disable ligatures as a reader
The cleanest solution is to switch to a font that does not use standard ligatures. Dyslexia-specific typefaces are a natural fit here: OpenDyslexic does not include standard ligatures - every letter retains its distinct, weighted form. Lexend and Atkinson Hyperlegible use minimal or no default ligatures, partly by design (both were created with legibility rather than typographic elegance as the primary goal). Switching to any of these fonts in your browser automatically eliminates the ligature issue along with providing the other readability benefits they are designed for.
LexiFont lets you apply any of these fonts to every website in Chrome with a single click. Because the font is applied at the browser level rather than the page level, it overrides whatever the site's CSS has set - including any ligature-active fonts the designer chose. This is the easiest way for a reader (as opposed to a developer) to remove ligatures site-wide.
Quick test: install LexiFont and set your reading font to Atkinson Hyperlegible or Lexend. Then revisit a page you found effortful and see whether the reading experience changes. If ligatures were part of the problem, the improvement will be immediate.
How to disable ligatures as a developer or designer
If you are building or maintaining a website and want to ensure your content is accessible to dyslexic readers, disabling standard ligatures in body text is a small, reversible CSS change:
body {
font-variant-ligatures: none;
font-feature-settings: "liga" 0, "calt" 0;
}
font-variant-ligatures: none is the higher-level property and is broadly supported. font-feature-settings provides lower-level control over individual OpenType features - setting "liga" to 0 disables standard ligatures, and "calt" to 0 disables contextual alternates, which in some fonts produce similar letter-joining effects.
The visual change is minimal for most readers. The fi pair will sit with the dot of the i intact rather than absorbed into the f. On a well-set page, this is barely noticeable. For a reader who was quietly stumbling over those merged shapes, it can meaningfully reduce friction.
This is one of the items on the dyslexia-friendly web design checklist that costs the least and disrupts the design the least. Unlike a font change or a colour-scheme overhaul, disabling ligatures is invisible to most of your audience and helpful to a meaningful portion of the rest.
If you use a CSS reset or utility framework, check whether it already sets font-variant-ligatures. Some modern resets (including parts of Tailwind's Preflight) reset certain font features to normal, which re-enables ligatures even if you have disabled them at a higher level. Set the rule on a specific selector if the cascade is fighting you.
What about decorative ligatures in headings?
The argument above applies primarily to body text - the paragraphs readers actually read through. Headings are a different case. A heading is typically read at a glance rather than decoded word by word, and the reader's eye spends only a fraction of a second on each character. Ligatures in headings rarely cause the kind of incremental confusion that accumulates over long-form reading.
If you want to keep ligatures in headings for aesthetic reasons while disabling them in body text, the CSS is straightforward:
body {
font-variant-ligatures: none;
font-feature-settings: "liga" 0, "calt" 0;
}
h1, h2, h3 {
font-variant-ligatures: common-ligatures;
font-feature-settings: "liga" 1, "calt" 1;
}
This is a reasonable compromise for sites that want to maintain a polished typographic identity in display type while keeping body text maximally legible for every reader.
Ligatures, font rendering, and the bigger picture
Ligatures are one piece of a broader set of font-rendering decisions that affect how easy or hard text is to decode. Antialiasing and font smoothing affect whether letterforms look crisp or blurry. X-height - the height of lowercase letters relative to capitals - determines how much visual space each character has to be distinctive. Serif versus sans-serif choices affect how much the letterforms blend into each other at the baseline.
None of these factors works in isolation, and the research on each one is messier than most guides admit. What is consistent is this: dyslexic readers benefit from text where every letter is as distinct as possible, as consistently rendered as possible, and as free from ambiguity as possible. Ligatures work against all three of these goals. They merge distinct characters into a combined shape, they make the same letter look different depending on its neighbour, and they introduce ambiguity about where one letter ends and another begins.
Disabling them is not a magic fix. If the underlying font is poorly chosen - too light a weight, too tight a letter-spacing, too small an x-height - removing ligatures will not compensate. But combined with a thoughtful font choice and sensible spacing, it is one more layer of friction removed. And removed friction compounds.
If you are a dyslexic reader looking for the fastest path to less effortful reading on the web, the practical answer is to use a tool like LexiFont Pro to apply a ligature-free, dyslexia-designed font to every site at once, rather than hoping individual websites have made these choices on your behalf. Most have not. That is not a criticism - ligatures are invisible to most readers and the accessibility implications are rarely taught in design curricula. It simply means that the control needs to sit with the reader.