Introducing: Ligatures-plus.js

A few months ago I ran across Chip Cullen’s absolutely fantastic ligatures.js – a very simple jQuery function that manually replaces character pairs or triplets with their corresponding unicode ligature. There was just one problem: to use the function, you had to manually test each of the characters you wanted to use against the target font. This is potentially a lot of work, especially if you have multiple custom fonts on your page.

So I built a wrapper that tests each of a user-selected set of ligatures against the font in a user-specified set of elements!

Get it & use it

Enabling the script on your site is straightforward. You’ll need jQuery running; you can download it here or use one of several content delivery networks – Google (Documentation), Microsoft (Documentation), or jQuery CDN – if you’d prefer not to host it on your own site.

Once you have jQuery running, include the ligatures-plus.js file. You can get it here:

General usage

Once you have included the file, you’ll just need to call the new jQuery function, presumably after the page has loaded. A typical usage might be as follows:

$(document).ready() function({

Note that by default, the script checks against all available unicode ligatures. If you want to check against a subset, you can change the value of var WHICH_LIGATURES. Available options are COMMON (ff, fi, fl), RARE (fff, ffi, ffl, ij, IJ, st), and ALL (all of the above).

You’ll also want to set the elements to run against. In the same section, set var ELEMENT = '[comma-separated list]' for the elements you want to use ligatures on.


Because the content may be loaded before Typekit or Google Fonts finish loading the fonts, it’s in your best interests to delay running the test until all your fonts have loaded. Gladly, Typekit and Google have made it easy to trigger functions on a webfont load event. Just run the ligature function in the handler for the Typekit font active event (as well as inactive, if you want), like so:

try {
      active: function() {
      inactive: function() { ... }
} catch(e) {}

How it works

I borrowed heavily from Chengyin Liu’s work on whatfont.js. The script creates a canvas, renders the ligatures in both the user-specified font and the default system serif/sans-serif font and compares them. If the system font ligature does not match the user-specified font, the ligature is rendered; otherwise it is ignored. At the end of the test, the canvas is removed.

Known issues

Flash when text restyles

Because the script is replacing HTML content, there is a flash similar to the one that occurs when loading a web-font (so you may actually get two flashes).

Changing HTML internals

If your selectors are too broad, you can mess up the internals of HTML. For example, if you run the script to include paragraph content, any link is subject to revision. For example, if you have a link like <a href="#first">link</a>, the “f i” in first may get converted to “fi” instead. The workaround now is to only use elements that do not have internal links or other HTML content that will get broken by the substitutions. Also, you can wrap your anchors around the tags to which you wish to add ligature support.

Obviously neither of these are optimal; I hope to use some pattern matching to prevent this issue in the future, but it’s a bit tricky because of some of the limitations in Javascript’s regular expression set. The lack of lookbehinds is particularly vexing in situations like this; it forces you to use negative lookaheads instead.

Default system fonts

By dint of the way the script works, you will not be able to render ligatures in the system default serif or sans-serif fonts. Unfortunately, I have yet to figure out a good way around this, because the system default fonts vary widely – they’re different on Windows, Mac, and Linux. Without doing some sort of additional processing involving OS sniffing (something I’d prefer to stay far away from), I have not yet discovered any good way to render ligatures in those fonts reliably.

Internet Explorer

Internet Explorer support is lacking at this point for all versions before IE9. Unfortunately, it doesn’t look like there will ever be a solution for this one. No older version of IE supports the canvas element, and the one project that aimed to deliver canvas support stalled or got stuck on some of the problems, one of the biggest being rendering fonts in the generated canvas elements. The function degrades gracefully, however: it simply won’t display any ligatures, so the page will look normal to the user.

Font families

The last potential stumbling block is size. The ligatures file itself is small, but font sets that actually include ligatures are not. Many of the fonts supplied by Typekit include two versions of their character set – one usually has ligatures and alternate glyphs; the other is the basic set. The extended set is often five to ten times larger than the other. The same will be true if you’re using @font-face embedding.

For that reason, you’ll want to be quite particular about which fonts and which elements you actually care about. On this site, for example, I’d love to have all the text supported, and I could: the fonts I’ve chosen all support ligatures. Unfortunately, if I included the extra character sets for all the headings and paragraphs, the font files would be over 2.5Mb, and that’s just much too large. I’m probably pushing it as is with support for just the headings.

Reporting issues

If you find a bug, please let me know by sending me an email: .

The future

My work

The first thing I want to do is fix this so that whatever tags are passed to the jQuery object are the tags used to pick ligatures. I may also add an optional parameter to the function to allow users to specify which ligatures to test for more easily. Once I have those things done, I’ll think about turning into a full-on jQuery plugin, as well as potentially creating WordPress and Blogger plugins for other, less technically savvy people to use.

At some point, I hope to add create some events that will prevent a flash from substituting the text, similar to the way Typekit does for loading webfonts. (As an aside, you can skip this problem if you are using Typekit’s events; the code I supplied above shouldn’t have this issue.)

Browser updates

Within the next two to three years, I hope to see the need for this script largely disappear. Firefox 4 and later already have some basic support to render OpenType font variants including ligatures (using -moz-font-feature-settings). Hopefully Webkit (both Safari and Chrome), IE, and Opera will all add support in the near future as well, at which point this tool can be happily retired.

Regardless of how the rendering technology develops, size constraints will still be an issue. I hoped that over the next few years, font providers will start enabling finer-grained control over which characters are included in the set. In my case, the only additional characters I am interested in right now are ligatures… but I get nearly a full megabyte worth of extra characters beyond that just to get them. Hopefully Typekit, Google Fonts, FontFont, and other font CDNs will take note, as will publishers of web font families. Optimally, web designers and developers should have fine-grained control – right down to the individual character.

Pipe up!

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