Java Base64 - Base64 Tools

java.util.Base64 (Java 8)

Java 8 provides java.util.Base64, which exposes static factory methods to obtain Base64 encoders and decoders that comply with RFC 4648 / RFC 2045. The class only contains static methods and returns different styles of Encoder / Decoder instances.

Variants (per spec)

Basic: uses the alphabet from Table 1 of RFC 4648 / RFC 2045; encoding does not insert line breaks; decoding rejects characters outside the Base64 alphabet.
URL and Filename safe: uses the URL‑safe alphabet from Table 2 of RFC 4648; encoding does not insert line breaks; decoding rejects characters outside the Base64 alphabet.
MIME: uses the alphabet from RFC 2045 Table 1; encoding wraps lines at ≤ 76 characters and uses CRLF (\r\n) as the separator; decoding ignores line separators and other non‑alphabet characters.

Method overview (selected)

Return type	Method	Description
Base64.Encoder	`getEncoder()`	Returns a Basic Base64 encoder.
Base64.Decoder	`getDecoder()`	Returns a Basic Base64 decoder.
Base64.Encoder	`getUrlEncoder()`	Returns a URL and filename safe encoder.
Base64.Decoder	`getUrlDecoder()`	Returns a URL and filename safe decoder.
Base64.Encoder	`getMimeEncoder()`	Returns a MIME encoder (wrap at 76 columns, CRLF as separator).
Base64.Encoder	`getMimeEncoder(int lineLength, byte[] lineSeparator)`	Returns a MIME encoder with custom line length and separator. Throws `IllegalArgumentException` if `lineSeparator` contains any Base64 alphabet character.
Base64.Decoder	`getMimeDecoder()`	Returns a MIME decoder.

Return type

Method

Description

Base64.Encoder

getEncoder()

Returns a Basic Base64 encoder.

Base64.Decoder

getDecoder()

Returns a Basic Base64 decoder.

Base64.Encoder

getUrlEncoder()

Returns a URL and filename safe encoder.

Base64.Decoder

getUrlDecoder()

Returns a URL and filename safe decoder.

Base64.Encoder

getMimeEncoder()

Returns a MIME encoder (wrap at 76 columns, CRLF as separator).

Base64.Encoder

getMimeEncoder(int lineLength, byte[] lineSeparator)

Returns a MIME encoder with custom line length and separator. Throws IllegalArgumentException if lineSeparator contains any Base64 alphabet character.

Base64.Decoder

getMimeDecoder()

Returns a MIME decoder.

Quick examples

import java.util.Base64; // Basic String encoded = Base64.getEncoder().encodeToString("hello".getBytes("UTF-8")); byte[] bytes = Base64.getDecoder().decode(encoded); // URL-safe String url = Base64.getUrlEncoder().encodeToString("a/b?c".getBytes("UTF-8")); // MIME (wrap at 76 columns) Base64.Encoder mime = Base64.getMimeEncoder();

Reference: Oracle Java SE 8 — java.util.Base64