Base64 Java Library

Base64 encoding and decoding of data from Java. Encode and decode methods for Strings, byte arrays, and streams.

Base64 is needed in many places other than its original use as an encoding format for transferring attachments in email. It can be used anytime binary or arbitrary data needs to be represented in common printable characters. For example to connect to a web page that requires a username and password (basic authentication) you need to Base64 encode the username and password.


Use base64 to add a basic authentication to an HTTP request

URL url = new URL("http://....");
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
    "Basic " + Base64.encode(
        username + ":" + password
InputStream in = connection.getInputStream();

Base64 is not Encryption

Be aware that Base64 encoding in not encryption. Base64 scrambles the output and it may appear to be unreadable, but it is easily deciphered by anybody with a little experience or time. Base64 encoded strings will often end in one or two equal signs, and they will have only letters, numbers, pluses, and slashes. Once somebody figures out that it is in Base64, it is just a matter of running the decode method on it. Furthermore, real encryption algorithms will change the entire output if one bit in the input changes. If you change a letter in a your message and then re-encode it with Base64, only a few characters will change. Base64 is not a substitute for encryption. Base64 used this way is obfuscation, and rather poor obfuscation at that. It may be a disservice to your users to use Base64 as obfuscation because it gives them the impression that their data is encrypted when it really isn't.

Command Line Program

To run Base64 as a stand alone program use the following command line:

java -classpath utils.jar com.Ostermiller.util.Base64 <files>
Base64 [-eldagxfqQvV] <files>
Encode or decode using the base64 format.
  If no files are specified standard input and output will be used.
  --help            Print this help message.
  --version         Print out the version number.
  --about           Print out license and contact info.
  -g --guess        Guess from contents whether to decode or encode. (default)
  -e --encode       Apply base64 encoding.
  -l --lines        Insert line breaks when encoding. (default)
  --nolines         Insert no line breaks when encoding.
  -d --decode       Remove base64 encoding.
  -a --decodeall    When decoding, attempt badly formatted files.
  --decodegood      Don't decode badly formatted files.  (default)
  -x --ext <ext>    File extension to use. (default: base64)
  -f --force        Overwrite files without prompting
  --noforce         Don't overwrite files.  (default)
  -v --verbose      Print a message for each file encoded or decoded. (default)
  -q --quiet        Print error messages.
  -Q --reallyquiet  Print nothing.


included languages:

  • English

Translations gladly accepted. Please translate You may want to use: Attesoro - A Java Translation Editor


Stephen Ostermiller com.Ostermiller.util.Base64Open source, GPLEncodes and decodes strings, byte arrays, files, and streams from static methods.
Robert W. Harder Base64Open source, public domainEncodes and decodes strings, byte arrays, and objects from static methods. It will encode and decode streams if you instantiate a Base64.InputStream or a Base64.OutputStream.
Roedy Green Java Glossary, com.mindprod.base64.base64Open source, freeware (except military)Encodes from byte arrays to strings, decodes from strings to byte arrays.
Tom Daley JavaWorld TipunknownAnnotated code and nifty graphic that shows how Base64 encoding works. Supports byte array to byte array operations.
Sinotar com.sinotar.algorithm.Base64Open source, free only for personal use.Encodes from byte arrays to strings, decodes from strings to byte arrays.