The short version
- A font file is a list of outlines, one per character, plus a table that says how wide each one is and how it sits on the line.
- TTF and OTF are two containers for the same idea. For a handwriting font the difference does not matter; everything opens both.
- The file does not contain pictures of your letters. It contains the shape of their edges, which is why it scales to any size without blurring.
- That is also why a faint or broken stroke in the photo becomes a hole in the font: the edge got traced wrong.
What is actually inside a font file
Open a font file in a text editor and you get noise, so people assume it is a picture of the alphabet. It isn't. A font file is a small database with a handful of tables. One table maps each character code (the letter a, the digit 7, a comma) to a shape. Another holds the shapes themselves. Another holds the numbers that say how wide each shape is, where its baseline sits, and how far it rises above and drops below the line. A few more hold the font's name and the licence text.
When you type, the app looks up each character, fetches its shape, draws it at the size you asked for, moves right by that character's width, and does it again. That is the entire job.
Outlines, not pictures
Each shape is stored as an outline: a closed path around the edge of the letter, made of straight lines and curves. A capital O is two paths, an outer ring and an inner one. The renderer fills the space between them. Because the file stores the edge rather than the pixels, the same letter draws cleanly at 8 points and at 800.
This is the part that matters if you are making a font from your handwriting. Whatever is in the photo gets traced into an edge. A stroke that is solid in the photo becomes a solid outline. A stroke that breaks up, because the ink was faint or the light was bad, becomes two outlines with a gap between them, and that gap is now permanent in every size.
The numbers that make it sit right
The outlines are only half of it. Three numbers per letter do most of the work of making a font feel like writing rather than a pile of shapes:
- Advance width: how far the cursor moves after this letter. Too wide and the words look gappy; too narrow and letters collide.
- Side bearings: the empty space on the left and right of the outline inside that width. This is what makes i andm feel evenly spaced despite being very different widths.
- Vertical position: where the outline sits relative to the baseline. Letters like g and y hang below it; everything else sits on it.
Font tools that read a sheet have to work all of this out from the picture. SnapFont takes them from your own writing: it measures where your letters actually sit on the sheet and how tall they are relative to each other, and uses that instead of forcing every letter into the same box. That is why the font sits evenly without you editing anything.
TTF vs OTF, in one table
| Feature | TTF | OTF |
|---|---|---|
| Full name | TrueType Font | OpenType Font |
| Age | 1991, Apple | 1996, Microsoft and Adobe |
| Curve type | Quadratic (simpler, more points) | Cubic, or TrueType inside |
| Ligatures and alternates | Supported | Supported, richer options |
| Opens in Word, Pages, Canva, GoodNotes, Cricut | Yes | Yes |
| Installs on iPhone via profile | Yes | Yes |
| Best for | Anything, especially screens | Type design with advanced features |
For a handwriting font the answer is that it does not matter. Every app you will use opens both. SnapFont exports TTF because it installs everywhere without a fuss, and Calligraphr offers either.
What this means for a handwriting font
- Ink quality decides outline quality. Dark, even strokes trace into clean edges. Faint ballpoint traces into fragments. The pen is the font.
- Each letter is one shape, forever. A font has no idea that you write a three different ways. Some tools add random variants to fake this; most handwriting fonts just live with it.
- Spacing is a separate craft. Nice letters with bad widths look wrong. Nice widths with average letters look fine.
- The file is small. A handwriting font with 72 characters is usually 20 to 60 KB. Email it to yourself.
If you want to see this end to end, the one photo walkthrough goes from pen to installed file in about twenty minutes.