Spline Font Database (.sfd)
The SFD (Spline Font Database) file extension is primarily used by FontForge, a font editing software. SFD files are ASCII-based, making them human-readable and easily transferable across the internet. They store comprehensive font data, including outlines, character data, and bitmap fonts. Introduced by FontForge, SFD files have evolved to support multiple layers and complex font features. This format facilitates detailed font design and editing, ensuring compatibility across various operating systems.