Base64 Encoder and Decoder in Java — Code Examples

Base64 encoding converts binary or text data into a 64-character ASCII alphabet so it can be safely transmitted over text-only channels. Here is how to encode and decode Base64 in each language using only the standard library.

Java 8+ includes java.util.Base64. Use getEncoder() for standard Base64 and getUrlEncoder() for URL-safe encoding.

import java.util.Base64;
import java.nio.charset.StandardCharsets;

public class Base64Example {
    public static void main(String[] args) {
        String input = "Hello, world!";

        // Encode
        String encoded = Base64.getEncoder()
            .encodeToString(input.getBytes(StandardCharsets.UTF_8));
        System.out.println(encoded); // SGVsbG8sIHdvcmxkIQ==

        // Decode
        byte[] decodedBytes = Base64.getDecoder()
            .decode("SGVsbG8sIHdvcmxkIQ==");
        String decoded = new String(decodedBytes, StandardCharsets.UTF_8);
        System.out.println(decoded); // Hello, world!

        // URL-safe (no + or /, with padding)
        String urlEncoded = Base64.getUrlEncoder()
            .encodeToString(input.getBytes(StandardCharsets.UTF_8));

        // URL-safe without padding
        String noPadding = Base64.getUrlEncoder().withoutPadding()
            .encodeToString(input.getBytes(StandardCharsets.UTF_8));
    }
}

• Always specify StandardCharsets.UTF_8 explicitly to avoid platform encoding surprises.
• Use getUrlEncoder() for JWT payloads and URL query parameters.
• getUrlEncoder().withoutPadding() matches the JWT specification.

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