Sifr

Sifr, often stylized as sIFR, is a web typography technique that replaces displayed text with Flash-rendered text in a chosen font. It emerged in the mid-2000s as a way to display non–web-safe fonts on websites before widespread support for web fonts via CSS.

How it works: A web page designates certain text to be replaced using CSS selectors. When the page loads, a small JavaScript library creates an embedded Flash object and passes the original text and font information to it. The Flash movie renders the text in the specified font and positions it in the page layout, effectively substituting the HTML text with Flash-rendered text. Fonts could be embedded with the library or hosted on the site.

Versions and usage: The technology evolved from early implementations to later versions that improved CSS integration and font handling. Sifr was popular for achieving distinctive typography on sites that could not rely on native font embedding at the time.

Limitations and decline: Sifr requires the Flash plugin, which limited accessibility, performance, and compatibility on devices or browsers with Flash disabled. The approach could hinder screen readers and search engine indexing, and it did not work well with dynamic content. With the rise of native web fonts via CSS @font-face and the eventual phase-out of Flash, the use of sIFR declined and is now largely obsolete. Modern web typography relies on CSS font embedding and formats such as WOFF and WOFF2.