A purpose-built 5x5 bitmap font for constrained displays, with 3x5 and 4x5 variants trading off glyph distinctiveness for compactness.
Key Takeaways
5x5 is the practical minimum for full ASCII legibility; narrower grids force sacrifices on M, W, dotted zero, and U/V/Y distinctiveness.
Real cell size is 6x6 or 4x6 once you add required character spacing, so advertised dimensions undersell actual pixel budget.
Spleen (5x8, effectively 4x8 with spacing baked in) is the community’s go-to alternative when you need complete ASCII coverage.
Subpixel rendering can push limits further: 1x5 fonts become viable on RGB LCD panels via millitext techniques.
Readability at 1:1 scale is the core failure mode for most tiny fonts; glyph design and spacing matter more than raw grid size.
Hacker News Comment Review
Consensus: 5x5 is a solid design but incomplete ASCII and misleading size labeling are real practical blockers for production use.
Active disagreement on whether 3x5 is usable: some find Robey’s 3x5 monospace acceptable, others call anything below 3x6 unreadable at a glance.
Commenters surfaced several alternatives with tradeoffs: Spleen 5x8, Gremlin-3x6, and C64-era 3x7 commercial 80-column fonts each solve different constraints.
Descender handling is the unsolved edge: you need 7-8 vertical pixels minimum for g/y to render distinctly, which no sub-6px font achieves.
Notable Comments
@FelipeCortez: subpixel rendering enables 1x5 fonts via msarnoff.org/millitext – useful for RGB LCD targets.
@ludocode: recommends Spleen 5x8 (glyphs effectively 4x8 with spacing) as the most complete tiny ASCII font available.
@kibwen: argues you need 7+ vertical pixels minimum once you account for uppercase height, lowercase x-height, and descenders – 5x5 is structurally incomplete.
@archargelod: after testing many 3x3 through 2x5 fonts for a game mod, found Gremlin-3x6 by zephram to be the only compact font that stays readable at 1:1.