Editing Base64 (section)

===Variants summary table===
Implementations may have some constraints on the alphabet used for representing some bit patterns. This notably concerns the last two characters used in the alphabet at positions 62 and 63, and the character used for padding (which may be mandatory in some protocols or removed in others). The table below summarizes these known variants and provides links to the subsections below.
{|class="wikitable" style="text-align:center"
! rowspan=2 | Encoding
! colspan=3 | Encoding characters
! colspan=3 | Separate encoding of lines
! rowspan=2 | Decoding non-encoding characters
|-
! 62nd
! 63rd
! ''pad''
! Separators
! Length
! Checksum
|-
! {{rh}} | {{nowrap|[https://datatracker.ietf.org/doc/html/rfc1421 RFC 1421]}}: Base64 for [[#Privacy-enhanced mail|Privacy-Enhanced Mail]] (deprecated)
| <code>+</code> || <code>/</code> 
| <code>=</code> || {{Yes}} || 64 || {{Yes}}, in PEM CRC || {{No}}
|-
! {{rh}} | {{nowrap|[https://datatracker.ietf.org/doc/html/rfc2045 RFC 2045]}}: Base64 transfer encoding for [[#MIME|MIME]]
| <code>+</code> || <code>/</code>
| <code>=</code> || {{Yes}} || 76 || {{No}} || {{No}}
|-
! {{rh}} | {{nowrap|[https://datatracker.ietf.org/doc/html/rfc2152 RFC 2152]}}: Base64 for [[#UTF-7|UTF-7]]
| <code>+</code> || <code>/</code>
|  || {{No}} || || {{No}} || {{Yes}}
|-
! {{rh}} | {{nowrap|[https://datatracker.ietf.org/doc/html/rfc3501#section-5.1.3 RFC 3501]}}: Base64 encoding for IMAP mailbox names
| <code>+</code> || <code>,</code>
|  || {{No}} || || {{No}} || {{No}}
|-
! {{rh}} | {{nowrap|[https://datatracker.ietf.org/doc/html/rfc4648#section-4 RFC 4648 §4]}}: base64 (standard){{efn|name=common|This variant is intended to provide common features where they are not desired to be specialized by implementations, ensuring robust engineering. This is particularly in light of separate line encodings and restrictions, which have not been considered when previous standards have been co-opted for use elsewhere. Thus, the features indicated here may be overridden.}}
| <code>+</code> || <code>/</code>
| <code>=</code> || {{No}} || || {{No}} || {{No}}
|-
! {{rh}} | {{nowrap|[https://datatracker.ietf.org/doc/html/rfc4648#section-5 RFC 4648 §5]}}: base64url (URL- and filename-safe standard){{efn|name=common}}
| <code>-</code> || <code>_</code>
| <code>=</code> optional || {{No}} || || {{No}} || {{No}}
|-
! {{rh}} | {{nowrap|[https://datatracker.ietf.org/doc/html/rfc9580 RFC 9580]}}: ASCII armor for [[#OpenPGP|OpenPGP]]
| <code>+</code> || <code>/</code> 
| <code>=</code> || {{Yes}} || 76 || {{Yes}}, (CRC24) || {{No}}
|-
! {{rh}} | Other variations
| colspan="7" | See {{section link||Applications not compatible with RFC 4648 Base64}}
|}
{{notelist}}