Base64 to Audio Decoder

Decoding Base64 Audio in 2026

Most modern Text-to-Speech APIs return audio as a Base64 string inside a JSON payload — it's the simplest way to deliver binary content over an HTTP API that demands JSON. To play that audio in a browser or save it to a file, you need to decode the Base64 back to raw bytes and either pipe those bytes to an <audio> element via a Blob URL, or write them to disk.

The challenge is usually format detection. APIs may return MP3, WAV, OGG, M4A, or even raw PCM depending on the model and the requested encoding. The data may or may not include a data URI prefix (data:audio/mp3;base64,…). And many copy-paste scenarios introduce stray whitespace, newlines, or surrounding quotes that break naive parsers.

What the Tool Does

1. Strips noise — data URI prefix, whitespace, newlines, surrounding quotes — to recover clean Base64.
2. Decodes the Base64 to a Uint8Array.
3. Detects the format by checking the first few bytes against known magic numbers: ID3 or FF FB for MP3, RIFF…WAVE for WAV, OggS for OGG, 1A 45 DF A3 for WebM, fLaC for FLAC.
4. Wraps in a Blob with the right MIME type and creates an object URL.
5. Plays + downloads via the browser's audio element and a download link.

Decoding Base64 Audio in Code

// Browser
const b64 = "...";
const bytes = Uint8Array.from(atob(b64), c => c.charCodeAt(0));
const blob = new Blob([bytes], { type: 'audio/mpeg' });
const url = URL.createObjectURL(blob);
audio.src = url;     // play in <audio>
// Or to download:
const a = document.createElement('a');
a.href = url;
a.download = 'output.mp3';
a.click();

// Node.js
import { writeFileSync } from 'fs';
writeFileSync('out.mp3', Buffer.from(b64, 'base64'));

// Python
import base64
with open('out.mp3', 'wb') as f:
    f.write(base64.b64decode(b64_string))

The reverse direction (audio file → Base64) is in our Audio to Base64 tool. For non-audio Base64, use the general-purpose Base64 Decoder.