The details that make it work

Know your modules.

Primary-source specifications, practical calculations and a clear line between a standard and a rule of thumb.

QR versions and capacity

Every standard version, every error correction level, and every published content mode.

Understand the blank border a QR scanner needs, with module-based measurements and a worked print example.

Compare QR levels L, M, Q and H, their approximate codeword restoration rates and the tradeoff with symbol density.

See how numeric, alphanumeric, byte and Kanji capacity differ, and why characters do not always equal bytes.

Learn how Micro QR differs from standard QR, including its smaller grid, quiet zone and limited capacity.

Understand the rectangular rMQR format, its narrow-space use cases and the need for a compatible reader.

Use contrast as a design warning, understand its limits and test the final QR artwork before printing.

Calculate a starting QR size from viewing distance, module count and print resolution, then test a physical proof.

Understand QR export dimensions, PNG DPI metadata and why vector modules help print workflows.

Review the generator's actual output settings, local processing limits, supported formats and verification boundaries.