what is the maximum amount of characters a base64string can contain

Question

I have a regex to validate if the string is a base64 string. I also check if the mimimum legnth of the base 64 string is 4 but what is the maximum length of characters a base64 string can contain??

I created a regex and added a mimimun atribute and added validation.

public class EndpointAddRequest : RequestBase
{
    [MinLength(4, ErrorMessage = "The number of characters is less than the minimum amount")]
    [RegularExpression(RegexConstants.Base64String, ErrorMessage = "Invalid AccessDevice Uid")]
    [Required(ErrorMessage = "AccessDevice uid is required")]
 }

https://stackoverflow.com/questions/13591616/what-is-the-maximum-length-of-base64-encoded-string-that-can-be-added-to-azure-q — mariusd96, Jan 03 '19 at 14:30
thnx i was already looking for it but couldn't find anything — Quent Wizle, Jan 03 '19 at 14:31
@DulauMariusCristian That is specific to Azure and is not applicable here. — , Jan 03 '19 at 14:31
This depends on how the base64 is stored. If this is stored in a string, the maximum length is discussed in this question: https://stackoverflow.com/questions/140468/what-is-the-maximum-possible-length-of-a-net-string — R Pelzer, Jan 03 '19 at 14:33
Possible duplicate of [Base64 length calculation?](https://stackoverflow.com/questions/13378815/base64-length-calculation) — Derviş Kayımbaşıoğlu, Jan 03 '19 at 14:41

score 2 · Answer 1 · edited Oct 07 '21 at 11:02

2

As far as I know there is no maximum length.

You can view the specification here.

edited Oct 07 '21 at 11:02

Community

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answered Jan 03 '19 at 14:30

Marie

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score 2 · Answer 2 · answered Jan 03 '19 at 14:32

There is no maximum. The minimum comes from the fact that Base64 encodes 3 input bytes into 4 on the output, plus padding if necesary. But there is no such limitation of how many characters can be encoded, as literally any byte stream (regardless or lenght) input is valid and will produce therefore an arbitrary long base64 output.

The practical limit is the amount of storage (either memory/disk/whatever) one has available, but the encoding itself doesn't place any restrictions.

what is the maximum amount of characters a base64string can contain

2 Answers2