---
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/es/changelog/2026-09-qr-colors-en/"
lang: "es"
---

# 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/es/changelog/2026-09-qr-colors-en/>

2026-09 · Colors and error correction

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

26 de septiembre de 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).

[Documentación técnica completa →](https://docs.qr3.app/en/api/codes/#colors-and-error-correction)

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