Editing Base64 (section)

=== Applications not compatible with RFC 4648 Base64 ===
Some applications use a Base64 alphabet that is significantly different from the alphabets used in the most common Base64 variants (see [[Base64#Variants summary table|Variants summary table]] above).

* The '''[[Uuencoding]]''' alphabet includes no lowercase characters, instead using ASCII codes 32 ("<code>&nbsp;</code>" (space)) through 95 ("<code>_</code>"), consecutively. Uuencoding uses the alphabet <span class="nowrap">"<code>&nbsp;!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_</code>"</span>. Avoiding all lower-case letters was helpful, because many older printers only printed uppercase. Using consecutive ASCII characters saved computing power, because it was only necessary to add 32, without requiring a lookup table. Its use of most punctuation characters and the space character may limit its usefulness in some applications, such as those that use these characters as syntax.{{citation needed|date=April 2016}}
* [[BinHex|'''BinHex 4''']] (HQX), which was used within the [[classic Mac OS]], excludes some visually confusable characters like '<code>7</code>', '<code>O</code>', '<code>g</code>' and '<code>o</code>'. Its alphabet includes additional punctuation characters. It uses the alphabet <span class="nowrap">"<code><nowiki>!"#$%&'()*+,-012345689@ABCDEFGHIJKLMNPQRSTUVXYZ[`abcdefhijklmpqr</nowiki></code>"</span>.
* A [[UTF-8]] environment can use non-synchronized continuation bytes as base64: <code>0b10<b>xxxxxx</b></code>. See [[UTF-8#Comparison with other encodings|UTF-8#Self-synchronization]].
* Several other applications use alphabets similar to the common variations, but in a different order:
** Unix stores password hashes computed with [[crypt (C)|'''crypt''']] in the [[passwd#Password file|<code>/etc/passwd</code> file]] using an encoding called <span id="B64">B64</span>. crypt's alphabet puts the punctuation <code>.</code> and <code>/</code> before the alphanumeric characters. crypt uses the alphabet "<code>./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz</code>" without padding. An advantage over RFC 4648 is that sorting encoded ASCII data results in the same order as sorting the plain ASCII data.
** The '''[[GEDCOM]]''' 5.5 standard for genealogical data interchange encodes multimedia files in its text-line hierarchical file format. GEDCOM uses the same alphabet as crypt, which is <span class="nowrap">"<code>./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz</code>"</span>.<ref>{{cite web|url=http://homepages.rootsweb.ancestry.com/~pmcbride/gedcom/55gctoc.htm |title=The GEDCOM Standard Release 5.5 |publisher=Homepages.rootsweb.ancestry.com |access-date=2012-06-21}}</ref>
** '''[[bcrypt]]''' hashes are designed to be used in the same way as traditional crypt(3) hashes, but bcrypt's alphabet is in a different order than crypt's. bcrypt uses the alphabet <span class="nowrap">"<code>./ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789</code>"</span>.<ref>{{cite web|url=https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libc/crypt/bcrypt.c?rev=1.1&content-type=text/x-cvsweb-markup|title=src/lib/libc/crypt/bcrypt.c r1.1|author-link=Niels Provos|first=Niels|last=Provos|date=1997-02-13|access-date=2018-05-18}}</ref>
** '''[[Xxencoding]]''' uses a mostly-alphanumeric character set similar to crypt, but using <code>+</code> and <code>-</code> rather than <code>.</code> and <code>/</code>. Xxencoding uses the alphabet <span class="nowrap">"<code>+-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz</code>"</span>.
** '''6PACK''', used with some [[terminal node controller]]s, uses an alphabet from 0x00 to 0x3f.<ref>{{cite web|url=http://private.freepage.de/cgi-bin/feets/freepage_ext/41030x030A/rewrite/alexs/xfr/flexnet/6pack_en/6pack.htm|title=6PACK a "real time" PC to TNC protocol|access-date=2013-05-19|archive-date=2012-02-24|archive-url=https://web.archive.org/web/20120224051938/http://private.freepage.de/cgi-bin/feets/freepage_ext/41030x030A/rewrite/alexs/xfr/flexnet/6pack_en/6pack.htm|url-status=dead}}</ref>
** [[Bash (Unix shell)|'''Bash''']] supports numeric literals in Base64. Bash uses the alphabet <span class="nowrap">"<code>0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@_</code>"</span>.<ref>{{cite web |title=Shell Arithmetic |url=https://www.gnu.org/software/bash/manual/html_node/Shell-Arithmetic.html |website=Bash Reference Manual |access-date=8 April 2020 |quote=Otherwise, numbers take the form [base#]n, where the optional base is a decimal number between 2 and 64 representing the arithmetic base, and n is a number in that base.}}</ref>