I would like to write a bash script to decode a base64 string. For example I type decode QWxhZGRpbjpvcGVuIHNlc2FtZQ== and it prints Aladdin:open sesame and returns to the prompt.

So far I have tried a simple bash file containing python -m base64 -d $1 but this command expects a filename not a string. Is there another non-interactive command (not necessarily in a Python module) that I can run from the command line to achieve this, without having to install any extra packages? (Or if I do, something super-minimal.)

  • 1
    Nice question. And thanks for your hint, I now know the python -m base64 -h can become handy.
    – RayLuo
    Commented Jan 27, 2021 at 0:34

8 Answers 8


Just use the base64 program from the coreutils package:

echo QWxhZGRpbjpvcGVuIHNlc2FtZQ== | base64 --decode

Or, to include the newline character

echo `echo QWxhZGRpbjpvcGVuIHNlc2FtZQ== | base64 --decode`

output (includes newline):

Aladdin:open sesame
  • 15
    Or: echo QWxhZGRpbjpvcGVuIHNlc2FtZQ== | base64 --decode && echo Commented Sep 4, 2014 at 16:08
  • 120
    Or: base64 -d <<< QWxhZGRpbjpvcGVuIHNlc2FtZQ==
    – jmk
    Commented Jul 29, 2015 at 11:23
  • 5
    echo QWxhZGRpbjpvcGVuIHNlc2FtZQ== | "C:\Program Files\Git\usr\bin\base64" --decode 2> nul > example.txt On Windows with git's base64.
    – Fire
    Commented Sep 19, 2016 at 18:03
  • 4
    @January It is not Just use, because many people know about the base64 program – but as one can't just insert a string as command line option, it is hard to get the syntax right for users who touch the CLI only once in a while.
    – feeela
    Commented Nov 15, 2016 at 14:04
  • 12
    On Mac, copy the the encoded string into clipboard and run pbpaste | base64 --decode. Commented Sep 21, 2017 at 11:15

openssl can also encode and decode base64

$ openssl enc -base64 <<< 'Hello, World!'
$ openssl enc -base64 -d <<< SGVsbG8sIFdvcmxkIQo=
Hello, World!

EDIT: An example where the base64 encoded string ends up on multiple lines:

$ openssl enc -base64 <<< 'And if the data is a bit longer, the base64 encoded data will span multiple lines.'
$ openssl enc -base64 -d << EOF
> QW5kIGlmIHRoZSBkYXRhIGlzIGEgYml0IGxvbmdlciwgdGhlIGJhc2U2NCBlbmNv
> ZGVkIGRhdGEgd2lsbCBzcGFuIG11bHRpcGxlIGxpbmVzLgo=
And if the data is a bit longer, the base64 encoded data will span multiple lines.
  • 14
    Thanks to Philippe's answer, you need to add -A for long base64 strings otherwise openssl will return nothing, see askubuntu.com/a/271676/305568
    – morloch
    Commented Oct 2, 2014 at 6:02
  • @morloch or just avoid removing the newlines from the base64 encoded data, and it works as expected...
    – geirha
    Commented Oct 2, 2014 at 7:56
  • 1
    I would not consider coreutils an "additional" package containing programs like ls, mkdir, cp, mv, and chmod. I doubt you can do anything useful with your machine without it.
    – vidstige
    Commented Jan 15, 2015 at 20:14
  • 1
    @vidstige, that's true. I don't know why I was under the impression that base64 was not installed by default; that is totally not the case.
    – geirha
    Commented Jan 16, 2015 at 14:26
  • 1
    While this is the ubuntu stack exchange, using openssl has the advantage over standard base64 of working in Git Bash on Windows, at least the older 1.8.1 Git Bash version I have installed.
    – willkil
    Commented Jun 16, 2015 at 23:05

Here you go!

Add the following to the bottom of your ~/.bashrc file:

decode () {
  echo "$1" | base64 -d ; echo

Now, open a new Terminal and run the command.

decode QWxhZGRpbjpvcGVuIHNlc2FtZQ==

This will do exactly what you asked for in your question.


With your original dependencies it is possible to do this with a minor modification to your original script:

echo $1 | python -m base64 -d

If you don't pass a file name, that python module reads from the standard input. To pipe the first parameter into it you can use echo $1 |.

  • 1
    Also: python -m base32 filename
    – kenorb
    Commented Nov 10, 2012 at 22:57
  • 1
    this does not work :) but use .b32* methods
    – rzr
    Commented Feb 16, 2014 at 11:11

I did comment base64 command line in http://wiki.opensslfoundation.com/index.php?title=Command_Line_Utilities. So I issue a Warning when using openssl base64 decoding :

 openssl base64 -e <<< 'Welcome to openssl wiki'


openssl base64 -d <<< 'V2VsY29tZSB0byBvcGVuc3NsIHdpa2kK'

Welcome to openssl wiki

warning base64 line length is limited to 64 characters by default in openssl :

 openssl base64 -e <<< 'Welcome to openssl wiki with a very long line
 that splits...'


openssl base64 -d <<< 'V2VsY29tZSB0byBvcGVuc3NsIHdpa2kgd2l0aCBhIHZlcnkgbG9uZyBsaW5lIHRoYXQgc3BsaXRzLi4uCg=='


to be able to decode a base64 line without line feed that exceed 64 characters use -A option :

openssl base64 -d -A <<<

Welcome to openssl wiki with a very long line that splits...

This is anyway better to actualy split base64 result in 64 characters lines since -A option is BUGGY ( limit with long files ).


Using perl

perl -MMIME::Base64 -ne 'printf "%s\n",decode_base64($_)' <<< "QWxhZGRpbjpvcGVuIHNlc2FtZQ=="

Or the same with python

python -m base64 -d <<< "QWxhZGRpbjpvcGVuIHNlc2FtZQ=="

Just to add another way to do it:

emacs -Q --batch  -eval '(princ (base64-encode-string (read-string ": ")))'

I had a few moments of hair-pulling on this one because the base64 Linux tool and also the openssl can decode, indeed. But I have this particular base64 encoded file that decodes to slightly wrong value. The few bytes do match, but then there is this presence of EF BF BD EF BF BD when I view in hexedit viewer. And then the next sequence of bytes match again when compared to the correctly decoded expected output. These weird sequence of bytes got inserted in the in-betweens, sometime as EF BF BD only.

To resolve the matter, I have to look how the Java sender encodes it and then I created a small java base64 decoder. And now I can decoded to the expected value.

Here is the small snippet that does it: https://gist.github.com/typelogic/0567cdab6c15487c31496cb90006ff52

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