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The “15%” figure for a QR code does not mean a sticker can safely cover 15% of its visible square. It refers to an approximate error-recovery rate measured in codewords, and it cannot predict whether a particular damaged code will scan. A small mark may disrupt reading, but the claim that erasing 0.7% always kills a QR code is not established as a general rule.
What the 15% figure actually measures
DENSO WAVE describes QR Code error correction as a ratio of total codewords, not a percentage of the code’s visible area. A codeword is eight bits. So the often-cited 15% for Level M is an approximate share of codewords that may be restored—not permission to cover 15% of the printed square with a sticker. DENSO WAVE’s error-correction explanation and its standardization page describe the measure this way.
QR codes use Reed–Solomon error correction: additional information is included with the original data so a decoder can recover some errors at the byte level. The available recovery capacity depends on the selected correction level and the amount of damage.
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How the four correction levels compare
| Level | Approximate recoverable share of total codewords |
|---|---|
| L | 7% |
| M | 15% |
| Q | 25% |
| H | 30% |
These are approximate codeword recovery rates published by DENSO WAVE, not safe coverage limits for stickers or other marks. DENSO WAVE says the appropriate level depends on operating conditions and QR Code size.
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Why a small damaged area can cause trouble
The percentage of visible area damaged is only one part of the problem. The location and shape of the damage matter, as do the code’s correction level and the conditions under which a scanner sees it. A mark that interferes with features the reader needs to locate or interpret the symbol can be more disruptive than a larger mark elsewhere. This is practical guidance, not a formula that predicts scan success.
DENSO WAVE warns that dirt or damage may exceed a code’s recovery capacity. Its FAQ also explains that deformation, including a tiny missing or smeared part, can make reading impossible or slow. That warning does not establish a universal failure point of 0.7% of the visible area. Its QR Code overview likewise describes recovery as dependent on the level of dirt or damage.
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Can you cover 15% of a QR code and still scan it?
Sometimes a damaged QR code may still scan, but the Level M figure alone cannot tell you whether a sticker covering 15% of a particular symbol will work. The percentage of codewords recoverable is not equivalent to the percentage of surface area that can be hidden. The outcome depends on the exact code, its correction level, what the sticker obscures, and the print and scanning conditions.
For the same reason, the assertion that erasing 0.7% of a QR code kills it needs a named code and reproducible test conditions. DENSO WAVE’s cited guidance warns that small damage can interfere with reading, but does not state 0.7% as a general failure threshold. Without those specifics, neither percentage is a reliable pass-or-fail rule for an individual code.
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