Adding a logo to a QR code is the single most common way to wreck a perfectly good code. It's also the single biggest reason a customized QR feels "designed" rather than generic. Here's how to add one without breaking scannability.
The 25% rule
Your logo should cover no more than 25% of the QR code's total area. Smaller is safer. The QR's built-in error correction can recover from up to ~30% damage at the "High" error correction level — your logo eats into that budget, so leave headroom.
A logo that's 25% by area is about 50% by side length on the visible square. That's bigger than most people realize. If your logo is 60%+ by side, scanning starts to fail intermittently.
Use a square, high-contrast logo
A square crop works best because the QR generator reserves a square in the center for the image. Round logos work if the surrounding white space is treated correctly — but you'll often get an awkward halo.
Contrast matters: a black logo on white background scans fine. A neon green logo on a yellow background does not. If your real brand logo has poor contrast, use a simplified high-contrast variant just for QR codes.
Use High error correction
QR codes have four error correction levels: L (7%), M (15%), Q (25%), H (30%). Most generators default to M. With a logo eating into the QR, you should bump to H. OneDollarQRcodes uses H by default for exactly this reason.
Keep it square and PNG/SVG with a transparent background
Save your logo as PNG-with-alpha or SVG before uploading. JPGs add a white box around the logo that interferes with the surrounding QR modules.
Test at print size
Print the QR at your final intended size, then scan with both an iPhone and an Android phone from arm's length. If both work cleanly, you're safe. If one struggles, shrink the logo by 20% and re-test.