fails due to storage size ?
Probably yes. I think you should change your question to "what is the max length of a string that a QR code supports".
You can refer to
wikipedia[
^].
Numeric only 7,089 3⅓ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Alphanumeric 4,296 5½ 0–9, A–Z (upper-case only), space, $, %, *, +, -, ., /, :
Binary/byte 2,953 8 ISO 8859-1
Kanji/kana 1,817 13 Shift JIS X 0208
A base64 string is used for encoding an image. If the image size is big, the length of the string may be greater than the limitation supported by QR code. Therefore, my suggestion is that don't convert a base64 string to QR code! No matter which SDK you use, ZXing, Dynamsoft Barcode Reader and so on, you may fail to encode the string.