How to Preview Kerning Pairs in FontForge

FontForge provides built-in tools to preview and adjust kerning pairs interactively in real time. By utilizing the dedicated Metrics Window, font designers can input custom character strings, view immediate spatial adjustments between glyphs, and manipulate kerning values either visually via drag-and-drop or by entering numerical values directly.

To access the real-time preview, open your font project in FontForge and navigate to the top menu, select Metrics, and click New Metrics Window (or press Ctrl + K on Windows/Linux, Cmd + K on macOS).

Once the Metrics Window opens, you can evaluate kerning immediately through several methods:

• Typing Text: Enter specific pairs (like "AV", "To", or "WA") or full test sentences into the text field at the bottom or top of the window. The preview pane updates instantaneously to show how the characters sit next to each other.
• Manual Dragging: Click on the vertical separator line between any two glyphs in the visual preview area. Dragging this line left or right increases or decreases the kerning value in real time, showing the immediate effect on the glyph spacing.
• Numeric Adjustments: Beneath each glyph, FontForge displays metric properties, including Left Side Bearing (LBearing), Advance Width (Width), Right Side Bearing (RBearing), and the Kerning offset (Kern). Changing the value in the "Kern" text box immediately recalculates the spacing in the preview above.

The Metrics Window also supports kerning classes (such as OpenType GPOS feature tables). When class-based kerning is enabled, modifying the distance between two representative glyphs will apply to the entire class, allowing you to preview the shared spacing across related letterforms immediately.

Additionally, you can change the preview point size in the Metrics Window to see how your kerning pairs render at both display and text scales.