How Much Data Can A QR Code Store?
Unlike traditional barcodes which are 1 dimensional, QR Codes are 2 dimensional allowing them to store a lot more data. The maximum amount of data a QR Code can store is 3Kb.
A QR Code is made of up multiple rows and columns. Each QR Code can contain up to 177 columns and 177 rows. These are seen by the naked eye as small squares, the combination of 177 columns and rows allows for a total of 31,329 squares. It's the arrangement of those squares in varying configurations that are able to store the data.
There are not 31,329 squares in every code. When a code is being created the generator determines the amount of data it needs to store and therefore the number of rows and columns needed to encode that data. If a QR Code contains more data, then you will generally find that it looks busier (more squares and generally smaller squares). Similarly, turning on Error Correction within a QR Code increases the amount of data stored in a code and therefore the complexity. Here are some examples.

In addition to storing the intended content of the QR Code, the code must also store positioning, timing, alignment, format, error correct and version data to ensure it can be read easily by a wide range of scanners. Thanksfully this is all built into the design of the QR Code and its only error correction that will subtract from the available 3Kb.
It’s a common misconception that adjusting the surface area of a code will allow you to include more data. This isn’t true as increasing the surface area of your code will not allow you to have more than 177 columns and rows and so simply stretches the code.
Keep Reading: 2. How Many Characters / Digits Can A QR Code Store??