A regular expression that matches a valid Base64 encoded string.
/^\s*data:(?:[a-z]+\/[a-z0-9-+.]+(?:;[a-z-]+=[a-z0-9-]+)?)?(?:;base64)?,([a-z0-9!$&',()*+;=\-._~:@/?%\s]*?)\s*$/i
What Is Base64:
Base64 is a group of binary-to-text encoding schemes that represent binary data (more specifically, a sequence of 8-bit bytes) in an ASCII string format by translating the data into a radix-64 representation.
The term Base64 originates from a specific MIME content transfer encoding.
Each non-final Base64 digit represents exactly 6 bits of data.
Three 8-bit bytes (i.e., a total of 24 bits) can therefore be represented by four 6-bit Base64 digits.
Base64 Data Example:
- data:image/gif;base64,xxxx==