Editing Base64 (section)

===Output padding===
Because Base64 is a six-bit encoding, and because the decoded values are divided into 8-bit octets, every four characters of Base64-encoded text (4 sextets = {{times|4|6}} = 24 bits) represents three octets of unencoded text or data (3 octets = {{times|3|8}} = 24 bits). This means that when the length of the unencoded input is not a multiple of three, the encoded output must have padding added so that its length is a multiple of four. The padding character is <code>=</code>, which indicates that no further bits are needed to fully encode the input. (This is different from <code>A</code>, which means that the remaining bits are all zeros.) The example below illustrates how truncating the input of the above quote changes the output padding:

<!-- This is the encoding of **THE WHOLE** of the above passage and the ending fits in with both the above encoding and the first line of the following example, verified using
http://www.motobit.com/util/base64-decoder-encoder.asp
In the previous version, the example started with a space, which was not visible and thus quite misleading. -->
{|class="wikitable"
! scope="col" colspan=2 | Input
! scope="col" colspan=2 | Output
! scope="col" rowspan=2 | Padding
|-
! scope="col" | Text
! scope="col" | Length
! scope="col" | Text
! scope="col" | Length
|-
| ''light {{bg|lightgrey|wor}}{{bg|#cef2e0|k.}}'' || 11
| {{mono|1=bGlnaHQg{{bg|lightgrey|d29y}}{{bg|#cef2e0|2=ay4=}}}} || 16
| 1
|-
| ''light {{bg|lightgrey|wor}}{{bg|#cef2e0|k}}'' || 10
| {{mono|1=bGlnaHQg{{bg|lightgrey|d29y}}{{bg|#cef2e0|2=aw==}}}} || 16
| 2
|-
| ''light {{bg|lightgrey|wor}}'' || 9
| {{mono|1=bGlnaHQg{{bg|lightgrey|d29y}}}} || 12
| 0
|- 
| ''light {{bg|lightgrey|wo}}'' || 8
| {{mono|1=bGlnaHQg{{bg|lightgrey|2=d28=}}}} || 12
| 1
|-
| ''light {{bg|lightgrey|w}}'' || 7
| {{mono|1=bGlnaHQg{{bg|lightgrey|2=dw==}}}} || 12
| 2
|}

The padding character is not essential for decoding, since the number of missing bytes can be inferred from the length of the encoded text. In some implementations, the padding character is mandatory, while for others it is not used. An exception in which padding characters are required is when multiple Base64 encoded files have been concatenated.