# `GSFont kerning(forFontMasterID:leftKey:rightKey:direction:)`

*Instance Method*

Kerning value for a pair of kerning keys.

## Declaration

```swift
func kerning(forFontMasterID fontMasterID: String, leftKey: String, rightKey: String, direction: GSWritingDirection) -> CGFloat?
```

## Discussion

Kerning keys are glyph identifiers or prefixed group keys such as `@MMK_L_A` and `@MMK_R_A`.

## See Also

### Kerning

- [`GSFont.kerningLTR`](/Core/GlyphsCore/GSFont/kerningLTR) — Left-to-right kerning data.
- [`GSFont.kerningRTL`](/Core/GlyphsCore/GSFont/kerningRTL) — Right-to-left kerning data.
- [`GSFont.kerningVertical`](/Core/GlyphsCore/GSFont/kerningVertical) — Vertical kerning data.
- [`GSFont kerningForDirection:`](/Core/GlyphsCore/GSFont/kerningForDirection:) — Kerning dictionary for a writing direction.
- [`GSFont masterKerning:direction:`](/Core/GlyphsCore/GSFont/masterKerning:direction:) — Kerning dictionary for one master and writing direction.
- [`GSFont kerning(forFontMasterID:firstGlyph:secondGlyph:direction:)`](/Core/GlyphsCore/GSFont/kerning(forFontMasterID:firstGlyph:secondGlyph:direction:)) — Kerning value between two glyphs in a master and writing direction.
- [`GSFont kerning(inMasterKerning:firstGlyph:secondGlyph:direction:)`](/Core/GlyphsCore/GSFont/kerning(inMasterKerning:firstGlyph:secondGlyph:direction:)) — Kerning value between two glyphs in a master kerning dictionary.
- [`GSFont setKerningForFontMasterID:leftKey:rightKey:value:direction:`](/Core/GlyphsCore/GSFont/setKerningForFontMasterID:leftKey:rightKey:value:direction:) — Sets the kerning value for a pair of kerning keys.
- [`GSFont removeKerningForFontMasterID:leftKey:rightKey:direction:`](/Core/GlyphsCore/GSFont/removeKerningForFontMasterID:leftKey:rightKey:direction:) — Removes the kerning value for a pair of kerning keys.
- [`GSFont setKerning:forMaster:direction:`](/Core/GlyphsCore/GSFont/setKerning:forMaster:direction:) — Replaces the kerning dictionary for one master and writing direction.
- [`GSFont addKerning:forMaster:direction:`](/Core/GlyphsCore/GSFont/addKerning:forMaster:direction:) — Adds kerning pairs to the kerning dictionary for one master and writing direction.
- [`GSFont masterIDforMetrics:`](/Core/GlyphsCore/GSFont/masterIDforMetrics:) — Returns the master identifier used for metrics and kerning data.
- [`GSFont masterIDforMetrics:hasLink:`](/Core/GlyphsCore/GSFont/masterIDforMetrics:hasLink:) — Returns the master identifier used for metrics and kerning data.
- [`GSFont.lastKerningChange`](/Core/GlyphsCore/GSFont/lastKerningChange)