RoboFont extension to compare font tables in two .otfs
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A RoboFont extension to diff-compare two OpenType font files.

  • Uses fontTools to extract font tables as .ttx files.
  • Uses Python’s difflib to make a diff between font tables.


  1. Download and unzip the extension package.
  2. Double-click the .roboFontExt file to install the extension in RoboFont.

…or get it via Mechanic.

Using the extension

  1. Use the Extensions menu in RoboFont to open the CompareOTFs dialog.
  2. Use the get font… buttons to select two OpenType fonts to compare.
  3. Use the get folder… button to choose a folder for the comparison output.
  4. Use the select tables… button to reveal a drawer with checkboxes for all supported OpenType tables.
  5. Use the checkboxes to select which tables you would like to compare.
  6. Use the compare fonts button to generate a set of diffs for the select tables.

Note: The more tables you select, the longer it will take for the script to build all files. Some font tables like CFF, CMAP or GPOS are particularly long.