Troubleshooting Bold Weight Rendering in FontForge

When an exported bold font renders with the wrong thickness, looks identical to the regular weight, or triggers artificial "faux bolding" in operating systems and applications, the issue typically stems from misconfigured metadata tables or path geometry inside FontForge. This troubleshooting guide provides clear, direct solutions to fix incorrect bold weight rendering by auditing your OS/2 weight metrics, style-linking flags, font identification naming, and outline construction.

1. Correct the OS/2 Weight Class

Operating systems rely on numeric values in the OS/2 table to determine a font’s visual weight. If this value does not match the actual design or standard conventions, applications will misrender the font.

  1. Open your font in FontForge and navigate to Element > Font Info.
  2. Select OS/2 from the left-hand menu, then go to the Misc tab.
  3. Locate Weight Class.
  4. Ensure the value is set to 700 (Bold). If you are designing an Extra Bold or Black weight, use 800 or 900 respectively. Do not leave it set to 400 (Regular).

2. Configure Style Linking and Style Map Flags

Style linking tells software which font file to activate when a user presses the bold shortcut (Ctrl+B or Cmd+B). If this is configured incorrectly, applications will either display the regular weight or apply an artificial, distorted bold.

  1. Go to Element > Font Info > OS/2 > TTF Values.
  2. Locate the Style Map (also known as fsSelection) settings.
  3. Check the Bold box. Ensure Regular and Italic are unchecked (unless it is a Bold Italic style, in which case check both Bold and Italic).
  4. Navigate to the Mac tab under Font Info and verify that the Mac Style is set to Bold.

3. Standardize Naming Conventions

Mismatched internal names frequently cause rendering engines to dissociate a bold weight from its font family, resulting in fallback rendering.

  1. Navigate to Element > Font Info > PS Names.
    • Fontname: Must be hyphenated without spaces (e.g., MyFont-Bold).
    • Family Name: Must match the rest of the family (e.g., MyFont).
    • Weight: Set explicitly to Bold.
  2. Navigate to Element > Font Info > TTF Names.
    • Family: MyFont
    • SubFamily: Bold
    • Full Name: MyFont Bold
    • Preferred Family: MyFont (Required if your family contains more than 4 core styles).
    • Preferred Styles: Bold

4. Remove Overlaps and Correct Path Direction

If the bold outlines contain overlapping paths or reversed path directions, font rasterizers can clip strokes or display counter spaces filled in black, making the weight appear distorted or poorly rendered on screen.

  1. Select all glyphs using Ctrl+A (or Cmd+A on macOS).
  2. Go to Element > Correct Direction to ensure all outer paths run clockwise and internal cutouts run counter-clockwise (or vice versa depending on OpenType/TrueType format rules).
  3. Go to Element > Overlap > Remove Overlap to unify layered strokes into single contours.
  4. Open Element > Validation > Find Problems to confirm there are no intersecting control points.

5. Clear System Font Caches for Testing

Operating systems and design tools aggressively cache font metadata. If you regenerate a font without clearing the cache, you may still see previous rendering errors even after fixing the settings in FontForge.

  • macOS: Clear the system cache via Terminal using sudo atsutil databases -remove, then restart your computer.
  • Windows: Stop the Windows Font Cache Service in services.msc, delete the .dat cache files inside C:\Windows\ServiceProfiles\LocalService\AppData\Local, and restart.
  • Alternative: Change the version number in Font Info > Revision by 0.001 every time you export during troubleshooting to force the OS to treat the file as a new font.