A minimal drawing canvas that stores strokes in the URL.

Live: https://draw.73.nu

• Draw freehand strokes on a full-screen canvas
• Pick color and thickness
• Undo strokes
• Fit the drawing to the current viewport aspect (without scaling existing strokes)
• Share the drawing by sharing the URL
• Download the current canvas as a PNG

• The drawing is stored in the URL hash (#…), not on a server.
• Each stroke is recorded as:
  • color (RGB)
  • thickness
  • a list of points
• Points are stored as normalized coordinates (0..1) and quantized to 16-bit integers. This keeps the data compact and resolution-independent.
• The full stroke list is serialized into a compact binary format (V3) and then encoded into the hash.
• V3 cuts binary size by ~43-45% over V2 (before compression) through:
  • Delta-encoded points: only the first point per stroke is absolute (2×uint16). The rest are stored as deltas from the previous point using zigzag varints, so small movements take 1-2 bytes per axis instead of a fixed 4.
  • Stroke deduplication: a flags byte marks whether color/thickness match the previous stroke. When they do, those bytes are skipped.
  • Varint counts: stroke and point counts use variable-length integers instead of fixed uint16.
• Old V2 URLs still load fine; the parser checks the version byte in the header.
• To keep URLs short, it chooses the smallest encoding among a few options (raw base64url, LZ-based compression, and optionally browser compression streams). The delta-encoded data also compresses better than V2 did, so real-world URL savings tend to be larger than the raw binary difference.
• On load (or when the hash changes), the page decodes the hash, rebuilds the stroke list, and redraws the canvas.
• The PNG download button exports the current canvas with toBlob (or toDataURL as a fallback).

• Because everything is in the URL hash, very complex drawings can hit browser and platform URL limits.
• Exported PNG size depends on the current viewport resolution.