Set Underline Position and Thickness in FontForge

Configuring the underline position and thickness in FontForge ensures that word processors and web browsers render underlines consistently and proportionally with your typeface design. This guide covers how to access the Font Info window, locate the appropriate font metrics, and input the correct values for underline height and vertical placement.

Step 1: Open Font Info

  1. Open your font project (.sfd) or font file in FontForge.
  2. In the top menu bar, click on Element.
  3. Select Font Info from the drop-down menu (or press Ctrl + Shift + F on Windows/Linux, or Cmd + Shift + F on macOS).

Step 2: Navigate to General Metrics

  1. In the left-hand sidebar of the Font Info window, select the General tab.
  2. Locate the fields labeled Underline Position and Underline Height (which represents the underline thickness).

Step 3: Set Underline Position and Thickness

  • Underline Position: Enter a value based on your font's coordinate units (usually based on an Em size of 1000 or 2048). Because the underline sits below the baseline, this value is almost always a negative integer (for example, -100 or -150). A larger negative number moves the underline further down from the baseline.
  • Underline Height: Enter a positive integer to define the stroke thickness of the underline (for example, 50). This typically matches or is slightly thicker than the standard stroke weight of your font's regular glyphs.

Step 4: Apply and Save

  1. Click OK at the bottom of the Font Info window to apply your changes.
  2. Save your FontForge source file by selecting File > Save.
  3. Export your updated font via File > Generate Fonts to embed the new underline parameters into the final OTF or TTF file.