---
title: "Colored QR codes and selectable error correction — via the API — qr3.app"
description: "The four image routes now accept foreground and background color, a transparent background and the error-correction level as parameters — on every plan."
canonical: "https://qr3.app/sk/changelog/2026-09-qr-colors-en/"
lang: "sk"
---

# Colored QR codes and selectable error correction — via the API — qr3.app

> The four image routes now accept foreground and background color, a transparent background and the error-correction level as parameters — on every plan.

Canonical: <https://qr3.app/sk/changelog/2026-09-qr-colors-en/>

2026-09 · Colors and error correction

# Colored QR codes and selectable error correction — via the API

26. septembra 2026

api print

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](https://docs.qr3.app/en/api/codes/#colors-and-error-correction).

[Kompletná technická dokumentácia →](https://docs.qr3.app/en/api/codes/#colors-and-error-correction)

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