OTF to SFD Converter

Convert OpenType fonts to editable Spline Font Database format online

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Editable Font Source

SFD stores font data in human-readable text, making it ideal for inspecting and modifying OTF glyph outlines, kerning, and metadata.

Round-Trip Workflow

Convert OTF to SFD for editing, then export back to OTF when done — a complete font modification pipeline using Convertio.

Secure Processing

Uploaded OTF fonts are deleted immediately after conversion. SFD output files are automatically removed within 24 hours for your protection.

How to convert OTF to SFD

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose sfd or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your sfd file right afterwards

About formats

OTF (OpenType Font) is a scalable font format jointly developed by Microsoft and Adobe, announced in 1996 and later standardized as ISO/IEC 14496-22. OpenType unifies TrueType and PostScript font technologies under a single container — OTF files with PostScript outlines use CFF/CFF2 tables for cubic Bezier curves, while those with TrueType outlines use quadratic splines in glyf tables (these typically carry the .ttf extension despite being OpenType). The format supports up to 65,535 glyphs per font, enabling comprehensive coverage of Unicode's vast character repertoire including Latin, Cyrillic, Arabic, CJK, and mathematical symbols within one file. Advanced typographic features are encoded in GSUB (glyph substitution) and GPOS (glyph positioning) tables, powering contextual alternates, ligatures, small caps, stylistic sets, and complex script shaping. A defining advantage is cross-platform consistency — the same OTF file renders identically on Windows, macOS, Linux, iOS, and Android without platform-specific builds. The rich OpenType Layout feature system is another major strength, giving designers fine-grained typographic control that was previously impossible in a single font file. OpenType 1.8 introduced variable font technology, allowing continuous interpolation across weight, width, slant, and custom design axes within a single compact file. Universal support in web browsers, design applications, office suites, and operating systems makes OTF the dominant professional font format in modern digital typography.
Initial release: 1996
SFD (SplineFont Database) is the native source file format of FontForge, the free and open-source font editor originally created by George Williams in 2000 under the name PfaEdit. The format stores a complete font project — glyph outlines (cubic and quadratic splines), advance widths, side bearings, hinting instructions, kerning and OpenType feature tables, naming records, and metadata — in a single human-readable text file. Each glyph is described by its Unicode code point, outline coordinates, reference composites, and anchors, making the entire font design inspectable and diffable with standard text tools. SFD functions as the editable working format during font development, from which finished fonts are compiled to binary formats like OTF, TTF, or WOFF. A primary advantage is version control friendliness — because SFD is plain text, font designers can track changes to individual glyphs, merge contributions from collaborators, and maintain full revision history using Git or any other VCS. The format's completeness is another strength: it preserves every piece of data that FontForge can represent, including TrueType instructions, contextual substitution lookups, and multiple master axes, avoiding round-trip data loss during editing. The SFD specification is publicly documented and has evolved through several versions. FontForge's widespread adoption in the open-source type design community means SFD serves as the source format for hundreds of freely licensed font families distributed worldwide.
Developer: George Williams
Initial release: November 7, 2000

Frequently Asked Questions

Why convert OTF to SFD?

SFD is a text-based font source format that makes glyph editing straightforward. Converting OTF to SFD lets you modify outlines, spacing, and metadata easily.

How do I open an SFD file?

SFD files are designed for font editing software. Open them in any application that supports the Spline Font Database format to access full editing capabilities.

Is all OTF data preserved in SFD?

Glyph outlines, metrics, and most metadata carry over. Some advanced OpenType-specific binary tables may be simplified in the text-based SFD representation.

Can I convert back from SFD to OTF?

Yes — SFD is an editable source format. After making changes, you can export back to OTF, creating a round-trip editing workflow via Convertio.

Is the conversion free?

Absolutely — Convertio converts OTF to SFD for free, entirely online. No desktop software or registration is required.

OTF to SFD Quality Rating

4.0 (15 votes)
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