# `GSFont masterIDforMetrics:`

*Instance Method*

Returns the master identifier used for metrics and kerning data.

## Declaration

```swift
func masterIDforMetrics(_ masterID: String) -> String
```

```objc
- (NSString *) masterIDforMetrics:(NSString *) masterID;
```

```python
masterIDforMetrics_(masterID: str) -> str
```

## Discussion

Linked masters can share metrics and kerning data with another master.

## 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 kerningForFontMasterID:firstGlyph:secondGlyph:direction:`](/Core/GlyphsCore/GSFont/kerningForFontMasterID:firstGlyph:secondGlyph:direction:) — Kerning value between two glyphs in a master and writing direction, or `NSNotFound` when no pair applies.
- [`GSFont kerningForFontMasterDict:firstGlyph:secondGlyph:direction:`](/Core/GlyphsCore/GSFont/kerningForFontMasterDict:firstGlyph:secondGlyph:direction:) — Kerning value between two glyphs in a master kerning dictionary, or `NSNotFound` when no pair applies.
- [`GSFont kerningForFontMasterID:leftKey:rightKey:direction:`](/Core/GlyphsCore/GSFont/kerningForFontMasterID:leftKey:rightKey:direction:) — Kerning value for a pair of kerning keys, or `NSNotFound` when no pair is stored.
- [`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:hasLink:`](/Core/GlyphsCore/GSFont/masterIDforMetrics:hasLink:) — Returns the master identifier used for metrics and kerning data.
- [`GSFont.lastKerningChange`](/Core/GlyphsCore/GSFont/lastKerningChange)