quality min font size

From MozillaZine Knowledge Base
Jump to navigationJump to search


With the move to the Cairo graphics backend, Mozilla’s text rendering code has changed significantly. Among the changes are support for advanced ligatures and smarter kerning. As these features are more computationally intensive than previous text rendering, they are only used at larger font sizes (where the quality difference is more noticeable), or when the text is affected by the CSS property text-rendering: optimizeLegibility.

This preference controls the minimum font size at which the high-quality rendering is used. Text below this size uses the high-speed path, and text at and above this size uses the high-quality path.

Possible values and their effects

A non-negative integer, specifying device pixels. Text rendered at this size or larger is optimized for display quality rather than display speed. Default is 20.


  • Text in chrome (the UI) is always rendered with the high-quality path.
  • Web pages can override the effects of this preference by specifying the text-rendering CSS property.

Recommended settings

To use the highest quality display and legibility settings for all rendered text, set this preference to 0. Conversely, setting this preference to a very high number will cause Mozilla to use the fastest rendering methods for all text.

First checked in

2007-07-26 by Robert O’Callahan

Has an effect in

  • Mozilla Firefox (trunk builds after 2007-07-26)
  • SeaMonkey (trunk builds after 2007-07-26)

Related bugs

External links