Font Face Observer
Font Face Observer is a small
@font-faceloader and monitor (3.5KB minified and 1.3KB gzipped) compatible with any webfont service. It will monitor when a webfont is loaded and notify you. It does not limit you in any way in where, when, or how you load your webfonts. Unlike the Web Font Loader Font Face Observer uses scroll events to detect font loads efficiently and with minimum overhead.
For details on how to use, check out the documentation.
Font Face Observer comes with three bundles:
- A CommonJS bundle (
dist/fontfaceobserver.cjs.js) for use in NodeJS:
npm install fontfaceobserver-es
var FontFaceObserver = ;var font = "My Family";font;
- An ES module bundle (
dist/fontfaceobserver.esm.js) for the above and also directly in the browser:
;const font = "My Family";font;
- A UMD build (
dist/fontfaceobserver.umd.js) mainly for browser without ES module support:
<script src=""></script><script>const font = "My Family";font;</script>
@font-face rules as usual. Fonts can be supplied by either a font service such as Google Fonts, Typekit, and Webtype or be self-hosted. You can set up monitoring for a single font family at a time:
const font = "My Family"weight: 400;font;
FontFaceObserver constructor takes two arguments: the font-family name (required) and an object describing the variation (optional). The object can contain
stretch properties. If a property is not present it will default to
normal. To start loading the font, call the
load method. It'll immediately return a new Promise that resolves when the font is loaded and rejected when the font fails to load.
If your font doesn't contain at least the latin "BESbwy" characters you must pass a custom test string to the
const font = "My Family";font;
The default timeout for giving up on font loading is 3 seconds. You can increase or decrease this by passing a number of milliseconds as the second parameter to the
var font = "My Family";font;
Multiple fonts can be loaded by creating a
FontFaceObserver instance for each.
var fontA = "Family A";var fontB = "Family B";fontA;fontB;
You may also load both at the same time, rather than loading each individually.
var fontA = "Family A";var fontB = "Family B";PromiseallfontA fontB;
If you are working with a large number of fonts, you may decide to create
FontFaceObserver instances dynamically:
// An example collection of font data with additional metadata,// in this case “color.”var exampleFontData ='Family A': weight: 400 color: 'red''Family B': weight: 400 color: 'orange''Family C': weight: 900 color: 'yellow'// Etc.;var observers = ;// Make one observer for each font,// by iterating over the data we already haveObject;Promiseallobservers;
The following example emulates FOUT with Font Face Observer for
var font = "My Family";font;
FontFaceObserver has been tested and works on the following browsers:
- Chrome (desktop & Android)
- Safari (desktop & iOS)
- Android WebKit
Font Face Observer is licensed under the BSD License. Copyright 2014-2017 Bram Stein and Damien Seguin. All rights reserved.