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About this tool
Convert local audio files into Base64 data URLs.
The Audio to Base64 converter turns an audio file into a Base64 data URL — the data:audio/mpeg;base64,… string you can paste directly into HTML, CSS or JavaScript instead of shipping a separate file. Encoding follows RFC 4648, which packs every 3 bytes into 4 characters, so the output is always 33% larger than the original. It is aimed at developers inlining short UI sounds, and at anyone who needs an audio clip embedded in a single self-contained file.
Open Audio to Base64 on AltFTool — it loads instantly in your browser.
Use the Audio file picker to choose an MP3, WAV, OGG or M4A clip up to 50.00 MB — the caption below reads 'Encoding…' and then switches to the filename, size and detected MIME type.
Read the Encoded data URL size panel: original size in bytes, Base64 characters, full data URL characters, padding characters (=), extra bytes on the wire, the MIME type, and a Safe to inline? verdict of Yes or Not recommended measured against 100.0 KB.
Press Copy result for the whole data: URL, Download .txt to save it as <filename>.base64.txt, or Reset to clear the encoder — the Result card also plays the clip and shows ready-made HTML, CSS and JavaScript snippets.
The file is read and encoded in the browser; nothing is uploaded to a server.
Reports Base64 length as 4 × ceil(bytes ÷ 3), the padding characters, and the full data URL length.
Flags anything over 100 KB, where a normal file URL beats a data URL on caching and seeking.
Exactly 33% bigger, plus up to 2 padding characters. Base64 encodes every 3 bytes as 4 characters, so a 480 KB MP3 becomes 640 KB of text — 4 × ceil(480000 ÷ 3) = 640,000 characters, plus about 23 characters for the data: prefix.
Only for short clips, roughly under 100 KB — UI chimes, click sounds, alert tones. Above that a data URL costs more than it saves: the bytes live inside your HTML, CSS or JS, so the browser cannot cache them separately, cannot range-request them for seeking, and must parse them before the page can finish loading.
It is the data URL syntax from RFC 2397: 'data:' then the MIME type, then ';base64' to say the payload is Base64 rather than percent-encoded, then a comma and the payload. Use audio/mpeg for MP3, audio/wav for WAV, audio/ogg for OGG and Opus, and audio/mp4 for M4A.
Not directly on this page: paste the data URL into the inspector below and it reports the declared MIME type, the exact decoded size in bytes, and the Base64 character count, which confirms the payload is well-formed, but it does not play or download the result. To decode a data URL into a playable, downloadable audio file, use the sister base64-audio-converter tool.
Add the Audio to Base64 widget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
<iframe src="https://www.altftool.com/embed/widget/audio-to-base64"
title="Audio to Base64 — free AltFTool widget"
width="100%" height="640" style="border:0;border-radius:12px;overflow:hidden"
loading="lazy" referrerpolicy="no-referrer-when-downgrade" allow="clipboard-write"></iframe>
<p style="font-size:12px;margin:4px 0 0">Widget by <a href="https://www.altftool.com/tools/all/audio-to-base64?utm_source=embed&utm_medium=widget" rel="nofollow">AltFTool — free online tools</a></p>