Comparison and Scenario Selection Guide for TTF, OTF, and WOFF2 Font Formats

TrueType, or TTF, uses quadratic Bézier curves to describe font outlines. A single outline segment requires more control points to draw a smooth curve. This outline mechanism has been used since the 1980s and is compatible with most desktop typesetting software.

OpenType, or OTF, supports cubic Bézier curves for describing outlines. A single smooth curve requires fewer control points, transitions between curves are more natural, and printing output has higher precision. OpenType was jointly launched by Adobe and Microsoft in 1996 and is compatible with TTF's quadratic curve specification.

WOFF2, the web font format, is implemented based on the Brotli compression algorithm. Compared with the DEFLATE compression used by the traditional WOFF format, it can reduce file size by approximately 30%. A smaller file size lowers web loading bandwidth usage and shortens first contentful paint time.

The WOFF format was released by W3C in 2009, and WOFF2 was launched in 2012. All current major global browsers, including Chrome, Firefox, Edge, and Safari 10 and above, provide native support, and no additional compatibility handling is required.

When front-end developers embed web fonts, follow the general format stack rule: declare WOFF2 first, then declare WOFF as a fallback. This configuration covers more than 99% of active desktop and mobile browser versions, and meets the requirements of most production scenarios.

Older versions of Internet Explorer only support EOT format. The current share of active IE users is less than 1%, so compatibility with this format is no longer required in most scenarios. If compatibility with older iOS devices is needed, you can additionally add TTF format as the final fallback layer.

Variable fonts are developed based on the OpenType 1.8 specification. A single font file can contain variation spaces for multiple weights, widths, and optical sizes. Designers and developers can adjust parameters to get font styles that meet requirements, and reduce the loading size of multiple files.

OpenType also supports multiple typesetting features, including standard ligatures, discretionary ligatures, and small caps, etc. These features can be enabled as needed during typesetting to improve text readability and visual aesthetics. Desktop typesetting software such as InDesign and Illustrator both support enabling these features.

When converting between different font formats, the outline data of the font remains unchanged. It will not alter the final displayed glyph shape, nor affect printing and display effects at large sizes.

The hinting information in fonts, which is optimization information for small text sizes on screens, may change during conversion between different formats. Small size text displayed on low-resolution screens may have subtle display differences. OKfmt provides a multi-format font conversion tool, and its conversion rules follow the standard logic of open source conversion libraries.