Editing Base64 (section)

===Decoding Base64 without padding===
Without padding, after normal decoding of four characters to three bytes over and over again, fewer than four encoded characters may remain. In this situation, only two or three characters can remain. A single remaining encoded character is not possible, because a single Base64 character only contains 6 bits, and 8 bits are required to create a byte, so a minimum of two Base64 characters are required: The first character contributes 6 bits, and the second character contributes its first 2 bits. For example:

{| class="wikitable"
! Length !! Encoded !! Length !! Decoded
|-
| 2 || {{mono|1=bGlnaHQg{{bg|lightgrey|dw}}}}
| 1 || ''light {{bg|lightgrey|w}}''
|-
| 3 || {{mono|1=bGlnaHQg{{bg|lightgrey|d28}}}}
| 2 || ''light {{bg|lightgrey|wo}}''
|-
| 4 || {{mono|1=bGlnaHQg{{bg|lightgrey|d29y}}}}
| 3 || ''light {{bg|lightgrey|wor}}''
|}

Decoding without padding is not performed consistently among decoders. In addition, allowing padless decoding by definition allows multiple strings to decode into the same set of bytes, which can be a security risk.<ref>{{cite conference |last1=Chalkias |first1=Konstantinos |last2=Chatzigiannis |first2=Panagiotis |title=Base64 Malleability in Practice |conference=ASIA CCS '22: 2022 ACM on Asia Conference on Computer and Communications Security |date=30 May 2022 |pages=1219–1221 |doi=10.1145/3488932.3527284 |url=https://eprint.iacr.org/2022/361.pdf}}</ref>