URL-Safe Base64 Encoding is suitable for scenarios where Base64 encoded results are transferred with the URL method. The basic process of this encoding method is first encoding content into a character string in Base64 format, then checking the resultant character string, substituting hyphens (-) for the plus signs (+) in the character string, and substituting the underscores (_) for the forward slashes (/).

• Basic Base64 alphabet
  

• URL-optimized Base64 alphabet (Differences are marked in red and feature the complete same algorithmic processing procedure)
  

• Algorithmic processing procedure
  

For the detailed encoding specifications, see the relevant descriptions in the RFC4648standard.