How to generate a QR code in Python

You need a QR code for a link, a poster, or your Wi-Fi network, and you want to make it from a script instead of an online tool. In Python, the qrcode library does this in two lines.

In this post, we will:

1. Install the qrcode library
2. Make a PNG from a URL
3. Set the size, border, and error correction level
4. Save an SVG for print
5. Make a Wi-Fi QR code

If you only need one QR code and don’t want to write any Python, I built Fast QR, a free QR code generator you can use instead.

Install the qrcode library

I recommend you do this inside a virtual environment. Run the following command:

pip install "qrcode[pil]"

The [pil] part also installs Pillow, which qrcode uses to make PNG images with custom colors. The examples in this post use qrcode 8.2, which needs Python 3.9 or newer.

Make a PNG from a URL

Create a file named make_png.py:

# filename: make_png.py

import qrcode

img = qrcode.make("https://cloudbytes.dev")
img.save("cloudbytes.png")

Run it:

python make_png.py

You should now have a cloudbytes.png file in the same directory. In my case it was 330 x 330 pixels. Scan it with your phone camera and it will open the URL.

qrcode.make() uses the default settings. To change them, use the QRCode class as shown in the next section.

Set the size, border, and error correction level

Create a file named custom_png.py:

# filename: custom_png.py

import qrcode

qr = qrcode.QRCode(
    version=None,
    error_correction=qrcode.constants.ERROR_CORRECT_H,
    box_size=20,
    border=4,
)
qr.add_data("https://cloudbytes.dev")
qr.make(fit=True)

img = qr.make_image(fill_color="black", back_color="white")
img.save("cloudbytes-large.png")

print(f"Version: {qr.version}")
print(f"Image size: {img.pixel_size} x {img.pixel_size} px")

Run it with python custom_png.py and you should see:

Version: 3
Image size: 740 x 740 px

Let’s see what each parameter does:

• version controls how many squares (called “modules”) the code has. It is an integer from 1 to 40, and version 1 is a 21 x 21 grid. Set it to None and call qr.make(fit=True) to let the library pick the smallest version that fits your data.
• box_size is how many pixels wide each module is.
• border is how many modules wide the quiet zone around the code is. The default is 4, which is the minimum the QR code specification allows, so don’t set it lower.
• fill_color and back_color set the module and background colors. They accept color names or RGB tuples such as (55, 95, 35).

The image size is (modules + 2 x border) x box_size. In our case, version 3 is 29 modules wide, so the image is (29 + 8) x 20 = 740 pixels.

Error correction levels

Error correction lets a scanner read the code even if part of it is dirty, damaged, or covered by a logo. The library has four levels:

Constant	Damage it can recover from
ERROR_CORRECT_L	About 7%
ERROR_CORRECT_M	About 15% (default)
ERROR_CORRECT_Q	About 25%
ERROR_CORRECT_H	About 30%

A higher level adds more modules for the same data. E.g. our URL fits in version 2 at the default level M, but needs version 3 at level H. The default M works for most codes. Use Q or H if the code is printed somewhere it can get damaged, or if you put a logo on top of it.

For more detail on how each level works, see QR code error correction explained on Fast QR.

Save an SVG for print

A PNG gets blurry when you scale it up. For posters, flyers, and anything else that goes to a printer, save an SVG instead. An SVG is a vector image, so it stays sharp at any size.

qrcode includes SVG image factories for this. Create a file named make_svg.py:

# filename: make_svg.py

import qrcode
import qrcode.image.svg

img = qrcode.make(
    "https://cloudbytes.dev",
    image_factory=qrcode.image.svg.SvgPathImage,
)
img.save("cloudbytes.svg")

Run it with python make_svg.py and open cloudbytes.svg in your browser to check it.

SvgPathImage draws all the modules as a single path, which the library documentation recommends because it avoids thin white lines between modules when you zoom in. It has no background, so everything except the dark modules is transparent. If you will print on a colored background, use qrcode.image.svg.SvgPathFillImage instead, which adds a white background.

The image_factory argument also works with the QRCode class, so you can combine it with the size and error correction settings from the previous section.

If you are not sure which format to use where, see PNG vs SVG for QR codes on Fast QR.

Make a Wi-Fi QR code

A Wi-Fi QR code lets guests join your network by scanning the code instead of typing the password. Android and iOS 11 or later both support it.

The QR code holds a plain text string in this format, documented on the ZXing barcode contents wiki:

WIFI:T:WPA;S:mynetwork;P:mypass;;

• T is the authentication type: WEP, WPA, WPA2-EAP, or nopass for an open network. Use WPA for a normal password-protected network.
• S is the network name (SSID).
• P is the password. Leave it out if T is nopass.
• H:true is optional. Add it if your network is hidden.
• The string ends with ;;.

The characters \, ;, ,, " and : must be escaped with a backslash if they appear in the SSID or password. The Wi-Fi Alliance registered the wifi URI scheme with IANA, and the formal definition is in section 7 of its WPA3 specification.

Create a file named wifi_qr.py:

# filename: wifi_qr.py

import qrcode


def escape(value):
    # Escape the backslash first, then the other special characters
    for char in ["\\", ";", ",", '"', ":"]:
        value = value.replace(char, "\\" + char)
    return value


ssid = "CloudBytes Guest"
password = "pa;ss:word"

payload = f"WIFI:T:WPA;S:{escape(ssid)};P:{escape(password)};;"
print(payload)

qrcode.make(payload).save("wifi.png")

Replace ssid and password with your own network details, then run python wifi_qr.py. With the example values, it prints:

WIFI:T:WPA;S:CloudBytes Guest;P:pa\;ss\:word;;

Notice that the ; and : in the password are escaped. Without the escaping, the scanner would read the password as pa and fail to connect.