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There are two reasons I use dynamic text replacement:

  1. Plain text in a browser window is never as smooth as it is in the design (except in Safari),
  2. The designs I'm given almost always use fancy (non-web based) fonts for headings, intro text etc.

Currently I subscribe to two solutions, both client-side: sIFR and cufón. If you want a quick answer to "what should I use?" then here it is: if you want replacement for long sentences and headings, use sIFR. If you want replacement for a few words on a button or in a menu, use cufón. If you want to know more, read on...


How sIFR works

sIFR uses javascript to dynamically embed a Flash object in the place of specified HTML text elements. The Flash object is essentially an empty SWF (compiled Flash file) which includes the characters of the font you want to use. When javascript embeds the SWF in the HTML, it passes the SWF arguments such as text-content, font-size, color, rollover behaviour and many more. Some of these properties javascript takes from the CSS applied to the text, and some are overridden by sifr-config.js, which is a human-readable config file containing additional formatting tweaks.

How to use sIFR

  1. Download the source (only sifr.js, sifr-config.js and sifr.css are actually needed).
  2. Generate a font SWF from a True Type Font file. You can do this manually with Adobe Flash (like this) but it is easier to use this online generation tool.
  3. Link to sifr.css in the head of your HTML page.
  4. Link to both scripts in the head of your HTML page, first sifr.js, then sifr-config.js
  5. Edit sifr-config.js to read in the font SWF you created and use CSS selector syntax to select the HTML text elements you want to replace.
  6. Tweak away in sifr-config.js until the text looks right when sIFR is both enabled and disabled, in case the user is missing Flash (iPhones don't have Flash as of early 2010!).


How cufón works

cufón is entirely javascript and works in all major browsers (including IE6). You still need to generate a font file, but this is output to a javascript file similar in size to the equivalent sIFR SWF font file. cufón looks at selected blocks of text and replaces each word with a dynamically generated image (using the HTML <canvas> tag), or in IE's case, a VML object (Vector Markup Language). As a consquence of this, increasing the text size of the page either doesn't affect cufón-replaced text or expands the image, blurring it. Except in IE, which scales the text perfectly.

How to use cufón

  1. Download the source (all you need is cufon-yui.js)
  2. Generate a font file from a True Type Font. You are unfortunately dependent on this online generator.
  3. Link to cufon-yui.js in the head of your HTML page. Beneath it, link to any font files you've generated.
  4. You may also want to create another file, cufon-config.js, to hold selector information much the same way as sifr-config.js does.
  5. Populate cufon-config.js with what HTML text elements you want to replace.


Font foundaries are seemingly run by people who are very freaked out that their fonts are going to leak for free. Hence, the vast majority of fonts can't legally be embedded directly into the CSS (what, you didn't know about that? It's been around a while in some form or another - the @font-face directive allows you to supply the font file for obscure font-families - but it's only legal with open source fonts).

Because sIFR uses Flash, and Adobe has a cordial agreement with the font foundaries in Switzerland (or wherever) which allows anyone to embed pretty much any font in a .swf, sIFR is totally legal. cufón... cufón not so much. Although both supply a compiled/obfuscated font resource in .swf/.js format respectively, and are basically the same from the font foundaries' point of view, they haven't got around to adding "Allows embedding using javascript methods" to their fonts' terms of use agreements. And I wouldn't count on it...

So in short, use cufón. Go on, it's young and fresh and rad! Push the font foundaries to legalise it! But remember: you read that in a blog post...I'm not going to be your lawyer if they come after you.


sIFR cufón
Core file-size (not including fonts) 30KB 18KB
Independent of Flash ×
Resizes nicely ×
Cursor-selectable text ×
Doesn't flicker on load ×
Independent of online font-generator ×
Online font-generator supports Open fonts (.otf) ×
Supported in all browsers
Degrades gracefully
Legal ×