Comparing QR Code Error Correction Levels

What Is QR Error Correction?

QR codes embed redundant data using Reed-Solomon error correction codes, allowing scanners to recover the original information even if part of the code is damaged, dirty, or covered by a logo. The QR standard defines four error correction levels, each offering a different trade-off between data recovery capacity and the amount of data the code can store.

The Four Levels

Level L (Low) — 7% Recovery

Level L recovers data if up to 7% of the code is damaged. It produces the smallest QR codes (fewest modules) because it devotes the least space to redundancy. Use Level L when the QR code will be displayed on a clean digital screen — website, app, or digital signage — where physical damage is unlikely.

Level M (Medium) — 15% Recovery

Level M is the default choice for most QR generators. It recovers from up to 15% damage, providing a reasonable safety margin for printed materials like business cards, flyers, and product packaging that may experience normal handling wear.

Level Q (Quartile) — 25% Recovery

Level Q handles up to 25% damage. It's appropriate for outdoor signage, warehouse labels, and industrial environments where codes may be exposed to moisture, dirt, or partial obstruction. The increased redundancy means the QR code needs to be larger (more modules) or must encode less data.

Level H (High) — 30% Recovery

Level H can recover from up to 30% damage. This is the required level when embedding a logo or image in the center of the QR code — the logo effectively 'damages' that region, and Level H ensures the remaining modules contain enough redundant data to reconstruct the full message.

Size and Density Trade-offs

Module Count Impact

Higher error correction levels require more modules (the small squares that make up the code). For the same data payload, a Level H code may need a QR version two or three steps higher than Level L. This means more modules packed into the same physical space, making each module smaller and harder to scan from a distance.

Data Capacity Reduction

At a fixed QR version (size), increasing error correction reduces the usable data capacity. For example, a Version 10 QR code (57x57 modules) can store 652 alphanumeric characters at Level L but only 367 characters at Level H — a 44% reduction in capacity.

Choosing the Right Level

Digital Display Only

Use Level L for the smallest possible code. Digital displays don't suffer from physical damage, and Level L produces codes that scan quickly due to their simplicity.

Standard Print Materials

Use Level M for business cards, brochures, event tickets, and product labels. It handles normal wear without making the code unnecessarily large.

Harsh Environments

Use Level Q for manufacturing labels, outdoor signage, and shipping labels. These codes may get wet, scratched, or partially covered.

Logo Embedding

Use Level H when placing a logo, icon, or design element over the QR code. Ensure the logo covers no more than 25% of the code area to stay within the error correction budget. Test the branded code with multiple scanning apps before mass production.

Testing and Validation

Always test QR codes under real-world conditions. Print the code at the intended size, simulate expected damage (fold, smudge, partial cover), and scan with at least three different apps. Camera quality varies dramatically across devices, and a code that scans instantly on a flagship phone may fail on an older device with a lower-resolution camera.