A fontstack is an ordered list consisting of a primary font and optional fallback font(s).
Fonts can only be set on symbol layer types. Set fonts from the Style tab of each symbol layer, under Text, in the Font input field. Each list of unique font pairings between primary and fallback font(s) will create a new fontstack.
An example fontstack:
"Open Sans Regular","Arial Unicode MS Regular"
When your primary font has missing glyphs, the text will be rendered in the fallback font instead. The default fallback font set by Mapbox Studio is Arial Unicode MS Regular. Unicode fonts include more glyphs than conventional fonts, allowing for better multilingual coverage.
Manage rendering time
The number of fontstacks paired with the density of text per zoom on your map can significantly slow down your map’s load time, especially when using multilingual labels. This is because dense multilingual text, at any set zoom level, will increase rendering time.
Here are some tips to minimize your map’s rendering time:
Latin scripts can handle more fontstacks, while other scripts like Chinese or Hangul, can require loading dozens of glyph tiles per fontstack.
Keeping labels sparse and spread across zoom levels allows for more fontstacks in your map style.
For multilingual maps with dense labelling, consider using fewer fontstacks.