Why are QR Codes with capital letters smaller than QR codes with lower case?

Take a look at these two QR codes. Scan them if you like, I promise there's nothing dodgy in them. Left is upper-case HTTPS://EDENT.TEL/ and right is lower-case https://edent.tel/ You can clearly see that the one on the left is a "smaller" QR as it has fewer bits of data in it. Both go to the same URl, the only difference is the casing. What's going on? Your first thought might be that there's a different level of error-correction. QR codes can have increasing levels of redundancy in order to make sure they can be scanned when damaged. But, in this case, they both have Low error correction. The smaller code is "Type 1" - it is 21px * 21px. The larger is "Type 2" with 25px * 25px. The official specification describes the versions in more details. The smaller code should be able to hold 25 alphanumeric character. But https://edent.tel/ is only 18 characters long. So why is it bumped into a larger code? Using a decoder like ZXING it is possible to see the raw bytes of each code. U ... Read full article.