How it works

sIFR is meant to replace short passages of plain browser text with text rendered in your typeface of choice, regardless of whether or not your users have that font installed on their systems. It accomplishes this by using a combination of javascript, CSS, and Flash. Here is the entire process:

1. A normal (X)HTML page is loaded into the browser.
2. A javascript function is run which first checks that Flash is installed and then looks for whatever tags, ids, or classes you designate.
3. If Flash isn't installed (or obviously if javascript is turned off), the (X)HTML page displays as normal and nothing further occurs. If Flash is installed, javascript traverses through the source of your page measuring each element you've designated as something you'd like "sIFRed".
4. Once measured, the script creates Flash movies of the same dimensions and overlays them on top of the original elements, pumping the original browser text in as a Flash variable.
5. Actionscript inside of each Flash file then draws that text in your chosen typeface at a 6 point size and scales it up until it fits snugly inside the Flash movie.

This all happens in a split-second, so all of the checking, replacing, and scaling is not visible to the user. It is not uncommon to notice a very short delay as the Flash loads, but to the user, none of the internals of this process are exposed.

* sIFR does not require any changes to the (X)HTML code, all the work is done by Javascript, Flash and CSS.
* If the user does not have Flash installed or Javascript enabled then the (X)HTML text is displayed and styled by CSS.
* sIFR is scalable, and when rendered will adjust to the users font size settings.
* sIFR is compatible with all screen readers. No problems or issues have ever been reported.
* sIFR text is selectable with the mouse, although visual confirmation of the selection may be absent when selected with body text.
* sIFR does not affect search engine placement or ranking, nor does it hide textual content from search engines or users.

The conclusion should be that sIFR is an accessible, mature technology, and that its use must be given serious consideration by designers and developers.

Loading speed

The rendering speed of the replaced text is an important consideration when using sIFR, and although speeds have been significantly increased since early versions, there can still be a distinct delay if there are many instances of sIFR on screen at one time. This is perhaps the best example of why using sIFR in moderation (ie. one headline per page, or headline per post) is currently the ideal way to use the technique.

This is one of the most frustrating drawbacks of using Flash replacement. The temptation when first implementing sIFR is to replace too many elements on the one page. For this to be viable, loading speeds have to be greatly increased; and although a nice nippy server will help you out, the true culprit is the time that the rather bulky Javascript takes to run.