Technical Term
Tofu (Rendering)
Slang for the empty box □ or question mark that appears when a system cannot render an emoji or Unicode character.
In-depth Analysis
"Tofu" is the informal term used by font engineers and emoji specialists for the rendering failure box (□ or ▯). It occurs when a device's font or OS does not include a glyph for a particular Unicode code point. New Unicode emojis often appear as tofu on older operating systems until an OS update includes the new glyphs. Google's Noto Font project — whose name literally means "No Tofu" — was specifically designed to eliminate these rendering failures across all scripts.