TTF and OTF are the two file extensions you meet most when working with fonts. In everyday use, .ttf usually means an OpenType font with TrueType (quadratic Bézier) outlines, while .otf often means an OpenType font with CFF/PostScript (cubic Bézier) outlines. Technically, though, the extension alone doesn't prove the outline format — software reads that from the font data itself. This article explains how the two curve types differ, why many designers prefer cubic curves while drawing, which outline format to export, and how these choices affect rendering across platforms — using FontCreator as the example throughout.

Intermediate / format basics. If you're just getting started, you can safely skip this page until you're ready to export. FontCreator handles the curve conversion for you, so the curve-format details below only become a practical decision when you build your final font files. Need just the short answer on what to export? Start with Which Font Format Should You Export?

Designing with cubic Bézier curves (PostScript)

• Familiarity with design tools. Many font designers prefer to draw glyph outlines using cubic Bézier curves, the foundation of PostScript outlines — especially designers used to vector design applications or to font editors that use PostScript-style outlines while editing. They behave like the curves in applications such as Adobe Illustrator, so they feel intuitive and familiar.
• Control and precision. A cubic Bézier curve is defined by two endpoints and two control points, giving more flexibility in shaping a curve. That extra control matters for complex glyphs where subtle adjustments make the difference.

TrueType curves: quadratic Bézier curves

• Quadratic simplicity. TrueType outlines use quadratic Bézier curves, defined by two endpoints and a single control point. They are mathematically simpler than cubic curves and are tied to TrueType's powerful hinting model. In practice, rendering quality and file size depend on the font, the rasterizer, the hinting, the conversion quality, and the target platform — a cubic-to-quadratic conversion can also increase the point count.
• Hinting advantages. TrueType's hinting model is highly sophisticated, allowing precise grid-fitting at small sizes so text stays legible and crisp. Hinting behaves differently across platforms, though. Windows rendering has traditionally relied more heavily on a font's TrueType instructions for small-size grid-fitting. Apple platforms generally lean more on their own rasterization for typical antialiased text, so built-in hinting may have less visible effect there — but it's too simplistic to say macOS and iOS ignore hinting entirely. Apple ships and actively maintains a TrueType hinting interpreter (rewritten for its Fall 2025 releases) and continues to support fonts that need hinting to render legibly.

One glyph, both curve types: the outer contour of this Q uses quadratic (TrueType) curves — a single off-curve control point per segment — while the inner counter uses cubic (PostScript/CFF) curves, with two control points per segment.

TTF vs OTF and the OpenType label

This is the short version. Whether a font is labelled TTF or OTF, it's almost always an OpenType font — the modern container that can hold TrueType (quadratic) or CFF/CFF2 (cubic) outlines. The extension is only a hint, not proof: software reads the actual outline format from the file's contents, not the filename. For the full terminology, history, and the table of internal font tables, see What's the Difference Between TrueType and OpenType Fonts?

Exporting fonts: choosing the outline format

• The .ttf / .otf misconception. Historically .ttf was associated with TrueType outlines and .otf with CFF (cubic) outlines, but .otf can also contain TrueType outlines — so the extension alone doesn't indicate the outline format.
• Conversion to TrueType. Because of TrueType's hinting model and broad compatibility, many designers export with quadratic curves even when they designed with cubic. FontCreator handles this conversion automatically on export.
• Exporting with cubic curves. Some designers prefer to keep the authored cubic outlines by exporting CFF-based OTF, avoiding cubic-to-quadratic conversion — though this needs more thought about the target platforms.
• Shipping more than one version. Some foundries ship both TrueType-outline and CFF-outline versions, but only when their users or target software actually benefit. For many projects, one well-tested export format is simpler and less confusing. CFF-based OTF files can be smaller — especially when subroutinization helps — but file size depends on the design, glyph set, hinting, compression, and export settings.

Tip: In FontCreator the curve type is chosen in Export Settings → Outline Format. See Export a Font for the full set of export options.

Variable fonts and curve considerations

• TrueType dominates variable fonts. Most variable fonts in circulation use TrueType outlines. One practical reason is fallback behavior: in a TrueType variable font, the default-instance outlines live in the standard glyf table, so older software that ignores the variation tables may still be able to use the default instance. CFF-based variable fonts use a new CFF2 table, which isn't backwards-compatible and requires CFF2-aware software — older CFF rasterizers cannot process it, so such fonts may not display at all on unsupported systems.
• Impact on design choices. The curve type affects a variable font's versatility and compatibility, so consider the target software and platforms the font needs to support.

Final thoughts

Many designers prefer the familiarity and control of cubic Bézier curves while designing; the decision on how to export — quadratic or cubic — depends on the intended use and the compatibility you need, particularly for variable fonts. Knowing how different operating systems handle hinting helps you make choices that display well across platforms. Hinting isn't the only cross-platform difference to watch, either: Windows and macOS also derive line spacing from a font's vertical metrics in different ways — see Font Metrics – Vertical Line Spacing for how to set those metrics so text lays out consistently everywhere.

Frequently asked questions

Is TTF or OTF better? Neither is universally better — both are OpenType fonts, and both TrueType-outline and CFF-outline fonts can carry advanced OpenType Layout features such as ligatures and small caps. CFF-based OTF files can be compact in some cases, while TrueType-outline fonts have the strongest native TrueType hinting model and are the usual choice for variable fonts. Choose by target use, compatibility, and export requirements — not by reputation.

Does the .ttf or .otf extension matter? Only as a compatibility convention. The extension doesn't determine the outline format; software should read the kind of outlines from the font's contents, so a given extension can hold either flavour.

Do TTF and OTF fonts work on Windows and macOS? Yes. Both are cross-platform OpenType fonts and work on Windows and macOS, although hinting is handled differently on each.

What to read next

• Export a Font — every Export Settings option, including Outline Format and CFF2.
• How to Make a Variable Font — building axes and masters.
• Font Metrics – Vertical Line Spacing — setting vertical metrics so line spacing stays consistent across Windows and macOS.
• What's the Difference Between TrueType and OpenType Fonts? — the format history and the TTF/OTF myth in full.