QR Code Error Correction Explained (L, M, Q, H)
By QRVane · Updated
QR codes include redundant data (Reed–Solomon error correction) so a scanner can rebuild the message even when part of the code is dirty, scratched or covered. You choose how much redundancy to add.
The four levels
L recovers roughly 7% of the code, M about 15%, Q about 25% and H about 30%. Higher levels survive more damage, but they add more modules, so the code gets denser and must be printed larger to scan well.
Which should you use?
M is a good default for clean digital use and print. Choose Q or H when the code will be exposed to wear (stickers, packaging, outdoor signs) or when you put a logo over the middle, because the logo hides modules the scanner has to reconstruct.
Error correction is not a licence to cover the code: the three large corner squares and the quiet zone around the edge must stay clear. And no level makes a tiny, low-contrast code scannable. Test the final print.