Colored QR codes and selectable error correction — via the API

The free generator on this site has always done colors. Through the API, every code was black on white. That changes now: the four image routes accept three new parameters.

What’s new

• fg — the module color, as a hex value like 1F4E79.
• bg — the background color, or transparent for an SVG without a background and a PNG with a real alpha channel.
• ecc — the error correction: L, M (default), Q or H. If you print on corrugated board or behind foil, use Q or H.

curl "https://qr3.app/v1/codes/r7f3Kx/qr.png?size=10&fg=1F4E79&bg=transparent" -o qr.png

SVG and PNG draw the colors right away. PDF and EPS already accept them but draw them only with one of the next releases; error correction applies to all four formats.

What matters in print

• Contrast: at least 4:1, dark modules on a light background. A dark blue like #1F4E79 reads well; a light orange like #ff6600 is already borderline.
• Transparent: the surface must be light and leave room for the quiet zone on all sides. On dark packaging, a dark code cannot be scanned.
• Error correction: it changes the module pattern, not the content. A printed code keeps working — but never mix old and new print files. A logo still forces the highest level, H.
• Before a large print run, always do a test scan on the real material.

What you need to do

Nothing. Without the new parameters, every code returns exactly the same bytes in all four formats as before. Invalid values are ignored; the route never answers with an error. Colors and error correction are available on every plan, including Free.

All details are under Colors and error correction.