What is AFM?

Adobe Font Metrics (AFM) is a text file describing Type 1 font metrics including character widths, kerning pairs, and bounding boxes.

What is SFD?

Spline Font Database (SFD) is the native project file format for FontForge, an open-source font editor for font design.

When Should You Use AFM vs SFD?

AFM vs SFD: Key Differences

• •AFM uses lossless compression while SFD uses lossless compression — both take the same approach to file size management.
• •Since both AFM and SFD use lossless compression, the quality characteristics are comparable — differences in file size come down to how efficiently each format implements compression.
• •Alpha channel support: SFD lacks transparency support.
• •AFM files are typically Very small, text-based metrics while SFD files range Larger than production fonts due to editing metadata
• •Use case fit: AFM targets postscript font metrics, pdf font embedding and SFD targets font design and editing, fontforge projects — your choice depends on which workflow stage you are serving.

Advantages of AFM

• ✓AFM applies lossless compression specifically calibrated for PostScript font metrics, PDF font embedding.
• ✓AFM enjoys broad native support across operating systems, browsers, and creative tools alike.
• ✓AFM guarantees every bit of the original data survives — no approximations, no shortcuts.
• ✓You will find AFM support built into virtually every tool that handles PostScript font metrics, PDF font embedding — no plugins or converters needed.

Advantages of SFD

• ✓At its core, SFD relies on lossless encoding — a design choice that makes it perfect for Font design and editing, FontForge projects.
• ✓You won't run into compatibility issues with SFD — it's a universal standard across platforms.
• ✓File size management with SFD: larger files guaranteed to match the original exactly.
• ✓Every major application in the Font design and editing, FontForge projects space supports SFD natively.

Common Use Cases for AFM to SFD Conversion

• Desktop publishing
• E-book formatting
• User interfaces
• Marketing materials
• Packaging design
• Signage systems

Industry Applications

Best Practices for AFM to SFD Conversion

• →Before converting AFM to SFD, review the font license — some licenses restrict format conversion
• →Check hinting data after conversion: SFD may handle TrueType hinting differently than AFM
• →Verify that all character sets (Latin, Cyrillic, CJK, etc.) survived the conversion intact
• →Test the converted font in both a browser and a desktop application
• →Keep the original font file in case the conversion alters spacing metrics

Troubleshooting AFM to SFD Conversion

• !SFD font doesn't render correctly → check if SFD supports all glyphs present in AFM
• !Licensing restrictions after AFM to SFD conversion → verify the font license allows format conversion
• !Hinting data lost converting AFM to SFD → some font formats like SFD may not preserve TrueType hinting
• !Special characters missing from converted SFD → font subsetting may have removed unused glyphs

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