The box character (□) is the official Unicode fallback for "I have no idea what to show here." It happens when the device's system font doesn't cover the specific Unicode block you're using.
Device Coverage Comparison
| Device / OS | Unicode Coverage |
|---|---|
| Windows 11 / macOS | Excellent |
| iOS / Android 10+ | Very Good |
| Android 6 and older | Limited |
Which Styles Are Safe?
- Safe: Mathematical Bold and Small Caps (supported since 2001).
- Risky: Runic and Gothic (missing from older Android fonts).
- Extreme: Obscure script blocks (Deseret, etc).
How to Fix It
The only solution is to switch to a style with wider compatibility. Mathematical Bold (𝐃𝐚𝐫𝐤𝐬𝐭𝐚𝐫) is the most reliable alternative that still looks stylish.