---
title: "Store colors on a QR code — with a contrast check — qr3.app"
description: "A code now remembers its print colors for SVG and PNG. The API checks the contrast, refuses unreadable pairs and warns about borderline ones."
canonical: "https://qr3.app/pl/changelog/2026-09-qr-colors-stored-en/"
lang: "pl"
---

# Store colors on a QR code — with a contrast check — qr3.app

> A code now remembers its print colors for SVG and PNG. The API checks the contrast, refuses unreadable pairs and warns about borderline ones.

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

2026-09 · Colors on the code

# Store colors on a QR code — with a contrast check

28 września 2026

api print

Until now, colors applied to a single download only: `?fg=1F4E79` on the
image URL. Now a code can remember its colors.

### What is new

```
curl -X PATCH https://qr3.app/v1/codes/qr_a1b2c3d4 \
  -H "Authorization: Bearer qr3_sk_..." \
  -H "Content-Type: application/json" \
  -d '{"appearance": {"foreground_color": "#1F4E79"}}'
```

- **Stored:** `foreground_color` and `background_color` (`#RRGGBB`, the
background also `transparent`). SVG and PNG draw them from now on without
any parameter; PDF and EPS follow with one of the next releases.

- **Parameters take precedence:** `?fg=000000` still returns the black print
file of the same code.

- **Error correction** stays a per-download choice (`?ecc=`) and is never
stored on the code.

### The contrast check

The API checks every color pair before it stores it:

- **Below 1.5:1** — white on white, for example — it refuses with `422`.

- **Borderline pairs** are stored and reported as a warning or as critical,
for example the brand orange `#F7901E` on white.

- **A transparent background** is always critical but never blocked: a light
code on dark packaging is allowed. The surface then has to provide the
contrast and keep a quiet zone of 4 modules free on every side.

### What you need to do

Nothing. Without stored colors every code returns the same bytes as before.
The MCP server knows the new fields; the color picker in the dashboard
follows.

If you embed an image: as long as a code had no colors, its image URL was
immutable for 24 hours. After the first coloring, an embedded URL without a
parameter of your own can therefore show the old image for up to 24 hours. A
parameter such as `?v=2` helps right away.

All details:
[Store colors on the code](https://docs.qr3.app/en/api/codes/#store-colors-on-the-code).

[Pełna dokumentacja techniczna →](https://docs.qr3.app/en/api/codes/#store-colors-on-the-code)

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