What actually changes when OTF becomes TTF
Most OTF files describe their letters with cubic curves, which have two control handles per segment. TrueType only understands quadratic curves, which have one. So a real OTF to TTF conversion has to redraw every curve in every glyph. Some converters skip this and rename the file, which leaves you with a ".ttf" that is still OpenType inside and still fails wherever TrueType was required.
Refont redraws each curve as a chain of quadratic segments that stays within one font unit of the original. A typical font is 1,000 or 2,048 units tall, so the difference is far below what you can see at any size.
Curves
Redrawn, not copied. Each one stays within 1 unit of the original, or 0.5 on Precise.
Hinting
CFF hints can't move into TrueType, so the TTF is unhinted. Current systems smooth unhinted fonts well; very small text on older Windows can look softer.
File size
Usually larger. Our 811-glyph test font went from 133 KB as OTF to 168 KB as TTF.
When you need TTF
- Microsoft Office
- Word and PowerPoint can embed TrueType fonts in a document but not CFF-based OpenType ones. If your document has to look the same on someone else's computer, use TTF.
- Cricut and Silhouette
- Both accept OTF officially, but on Windows TTF fonts tend to show up more reliably in the design software. If an OTF installs but never appears in the font list, try the TTF.
- Watch faces and Android apps
- Many watch-face builders and Android font apps only accept TTF files.
- Older software
- Some older design, embroidery and signage programs predate OpenType CFF support.
You may not need to convert at all. Canva, Procreate, Kindle and macOS all accept OTF as it is, and for a website the right format is WOFF2, not TTF.
Standard or Precise?
The accuracy setting is the largest distance, in font units, that a rebuilt curve may stray from the original. Standard (1 unit) is the same default professional font tools use and is right for almost everything. Precise (0.5 unit) uses more points to follow the original more closely, which makes the file slightly larger. Choose it for fonts that will be printed very large, like signage or display type.
Changing the setting re-runs any TTF conversions already in the list, so you can compare the two sizes.
Limits
- Variable OTF fonts (CFF2) can't be converted to TTF yet. Convert a single weight of the family instead.
- Hinting is never carried over, as explained above. The report says so on every file.
- Collections (TTC/OTC) need splitting first. Drop the collection on the homepage converter and choose "Split to TTF / OTF".
Check your font license first. Many commercial licenses don't allow format conversion. Refont reads the font's embedding setting and warns you, but only your license has the final word. How font licensing works
How we tested this
We converted a commercial 811-glyph OpenType font, a 4,503-glyph TrueType font (Arial, in the other direction), and a PostScript Type 1 font, then compared every glyph's bounding box with the original. The largest difference was about 0.1 font unit. The glyph count, kerning and OpenType features matched in every case, and each output opened cleanly in fontTools, the library font foundries use to build fonts.
The conversion itself runs on fontTools too, compiled for the browser. That engine is about 7.5 MB, so the first OTF to TTF conversion of a visit takes a few seconds longer while it loads. Your browser keeps it afterwards.