A Guide to OpenType Features

In Figma, you first have to open the Type Settings menu (the button with the three dots in the bottom corner of the Text panel). In the Type Settings pop-up window, navigate to the Details tab, where you will find a list of checkboxes you can play with to tweak the appearance of the type. Though not clearly labeled, most of them – for example Number Styles, Fractions, Ligatures, and Stylistic Sets – refer to OpenType features.

In Adobe InDesign, you can find the OpenType features in the Character window. Click the options button (the one with the menu icon) in the top right corner of this window and then navigate to the OpenType submenu. There you will find the whole list of available Opentype features, including Stylistic Sets, multiple number formats and more. Note that the “Ligatures” option can be found outside of the OpenType submenu, despite being a feature too.
You can also check out the alternates for each glyph by selecting it with the text tool. If a character has alternates, a small dropdown with thumbnails of the alternate glyph will apear under it. Selecting it won't activate the corresponding OpenType feature, though, and the appearance of the character won't change anywhere else in the text. So use this feature carefully!

In Adobe Illustrator, the OpenType features have their own dedicated panel window. There you will find dropdowns and buttons for the most commonly used features, that we'll explain in detail in the section below.
Just like in InDesign, you can check out the alternates for each glyph by selecting it with the text tool too. If a character has alternates, a small dropdown with thumbnails of the alternate glyph will apear under it. Selecting it won't activate the corresponding OpenType feature, though, and the appearance of the character won't change anywhere else in the text. So use this feature carefully!

Ligatures are the most common type of alternate accessible through OpenType features. They have been a part of typography for centuries, and in modern font software they exist in 2 variants:

Standard ligatures ("liga") are the ones that the type designer intends to be active at all times. They will balance the white space and avoid collisions in tricky pairs like “fi”, and are active by default in most design software and browsers.

Discretionary ligatures ("dlig") are usually rooted in historical shapes and will add a more expressive or calligraphic touch to the typography. They will only appear when the feature is activated.

Numerals can also have stylistic variations just like letters — think of Diatype with options for alternate 1, 3, 4, 6 and 9 😅. But they also have a number (no pun intended) of dedicated OpenType Features for all possible use cases and preferences.

Traditionally, the numerals were drawn to blend nicely with lowercase letters in text, and they did so by aligning the heaviest, most important part of the digit with the letters, and pushing the rest to the ascenders and descenders. These numbers, which are now called "oldstyle", are more common in serif fonts and text-heavy layouts (or as a classical touch), and can be accessed through the Oldstyle Figures ("onum") feature.

Later, with advertising, it became more common to align the numbers with the capital letters for more compact and punchy headlines. These numbers, which we know from most modern sans-serif fonts, are called "lining" and, if not set by default, can be accessed through the Lining Figures ("lnum") feature.

Another useful feature for numbers is Tabular Figures ("tnum"). In this variant, all the numbers occupy the same width, which is especially useful for tables, lists, and UIs with variable data, where you want to keep the same width no matter what the numbers are.

Have you ever tried to read a code or password and couldn't figure out if that round symbol was a zero or an uppercase O? That's what the Slashed Zero ("zero") feature is for. Check your password manager (you should use one) or code editor and see it in use.

And for the number geeks out there, there are still other useful OpenType Features to talk about. Fractions ("frac") are useful for cake recipes and non-metric DIY tutorials (but not for birthdays). Subscript ("subs") numbers are useful for your chemistry homework; and Superscript ("sups") is the perfect feature for math formulas and referencing footnotes in a book or Wikipedia article.