QR Code Error Correction Levels: Choosing the Right One

How Error Correction Works

QR codes use Reed-Solomon error correction, a mathematical technique that adds redundant data to the code. When part of the QR code is damaged, obscured, or missing, the redundant data allows the decoder to reconstruct the original information.

The Four Levels

Level L (Low): ~7% recovery. Smallest QR code for a given data payload. Best for clean, controlled environments like digital screens. Level M (Medium): ~15% recovery. The default choice for most applications — good balance between size and resilience. Level Q (Quartile): ~25% recovery. Suitable for outdoor use, packaging, and environments with moderate wear. Level H (High): ~30% recovery. Required when placing logos over the QR code center or when expecting significant damage.

Size vs Resilience Tradeoff

Higher error correction means more modules (black/white squares) in the QR code. A URL encoded at Level L might fit in a Version 3 QR code (29x29 modules), while Level H of the same URL might require Version 5 (37x37 modules). Larger QR codes need to be printed bigger to remain scannable.

When to Use Each Level

Level L: Digital displays, receipts (single use), data-dense applications where size must be minimized. Level M: Standard printed materials, business cards, flyers. Level Q: Product packaging, labels that may be scratched or dented, outdoor signage under cover. Level H: Branded QR codes with logos, outdoor posters, industrial labels, harsh environments.

Testing Methodology

Print your QR code at the intended size and scan it with at least three different phone models. Then simulate damage: cover 10%, 20%, and 30% of the code area with tape and re-scan. The code should remain scannable up to the damage threshold of your chosen error correction level.