Developing fonts > Specifications

Baseline tags

This section defines the standard OpenType Layout baseline tags that Microsoft supports. A registered baseline tag has a specific meaning when used in the horizontal writing direction (used in the 'BASE' table's HorizAxis table), vertical writing direction (used in the 'BASE' table's VertAxis table), or both, and conveys information to font users about a baseline's use. For example, the "romn" baseline tag is commonly used to identify the baseline to layout Latin text in the horizontal, vertical, or both directions for Latin text layout. For compatibility and ease of use, Microsoft encourages font developers to use registered baseline tags.

This version of the Tag Registry identifies the baselines that Microsoft has implemented to date. All baseline tags are 4-byte character strings composed of a limited set of ASCII characters in the 0x20-0x7E range. Baseline tags consist of four lowercase letters.

Baseline Tag	Description
hang	Hanging baseline
icfb	Ideographic character face bottom edge baseline
icft	Ideographic character face tope edige baseline
ideo	Ideographic em-box bottom edge baseline
idtp	Ideographic em-box top edge baseline
math	Mathmatical centered baseline
romn	Roman baseline

this page was last updated 16 November 2004