The error correction level of a QR Code determines how much damage the code can sustain and still be readable. Each QR Code has one of the four levels of error correction. These are :

Low - L

Medium - M

High - Q

Highest - H

The recommended error correction level for printing a QR Code depends on the intended use and the printing quality.
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Keeping the error correction at the Highest (H) for individual QR Code downloads is recommended.

A lower error correction level may be enough if the QR Code is printed on a high-quality printer, such as a commercial printing press. In this case, an error correction level of L or M should be adequate.

However, if the QR Code will be printed on a lower-quality printer or on a material that may be subject to damage, such as a label or a package, it is recommended to use a higher error correction level. In this case, using an error correction level of Q or H will provide better protection against damage.

How does the error correction level affect the size of the QR Code?
Using a higher error correction level will increase the size of the QR Code, so if the size of the code is a concern, it may be necessary to balance the error correction level with the desired size of the code. The minimum recommended size for printing a QR Code is 2 x 2 cm (0.8 x 0.8 inches).

Lowering the error correction level of a QR Code makes it less dense. Hence, it lowers the maximum printing size of a QR Code. The higher the error correction level, the more wear-and-tear it can sustain before it becomes unscannable.

While having as much error correction as possible is ideal, higher levels require more modules. Larger module configurations require a larger area/QR Code size for better scannability. If there are severe size constraints, choosing Level L, where only 7% of the data is retrievable, is ideal.