Convert MP3 to M4A

Turn MP3, the universally supported compressed audio format, into M4A, AAC audio in an MP4 container, the iTunes and Apple Music standard. FileChanger runs the audio conversion in one call, no local tooling to install.

In the browser

Upload a file and download the result, no pipeline required. Open the converter.

One API call

POST the file with from=mp3 and to=m4a, get the converted bytes back. Jump to the code.

From an agent

FileChanger ships an MCP server, so agents can run this conversion themselves. See the docs for setup.

Uploading something you care about? How to convert files safely explains what to check before you trust any converter, and Security and data handling describes exactly what we store and for how long.

Convert MP3 to M4A in code

The same call from any language: POST the file to /api/convert, the response body is the converted file.

curl -X POST https://filechanger.io/api/convert \
  -H "X-Api-Key: fc_your_api_key_here" \
  -F "file=@input.mp3" \
  -F "from=mp3" \
  -F "to=m4a" \
  -o output.m4a

import requests

with open("input.mp3", "rb") as f:
    response = requests.post(
        "https://filechanger.io/api/convert",
        headers={"X-Api-Key": "fc_your_api_key_here"},
        files={"file": f},
        data={"from": "mp3", "to": "m4a"},
    )

response.raise_for_status()
with open("output.m4a", "wb") as out:
    out.write(response.content)

const formData = new FormData();
formData.append("file", fileInput.files[0]);
formData.append("from", "mp3");
formData.append("to", "m4a");

const response = await fetch("https://filechanger.io/api/convert", {
  method: "POST",
  headers: { "X-Api-Key": "fc_your_api_key_here" },
  body: formData,
});

const output = await response.blob();

import java.net.http.HttpRequest.BodyPublishers;
import java.net.http.HttpResponse.BodyHandlers;
import java.nio.file.Path;

String boundary = "----FormBoundary" + System.currentTimeMillis();
byte[] fileBytes = java.nio.file.Files.readAllBytes(Path.of("input.mp3"));

String body = "--" + boundary + "\r\n"
    + "Content-Disposition: form-data; name=\"file\"; filename=\"input.mp3\"\r\n"
    + "Content-Type: application/octet-stream\r\n\r\n"
    + new String(fileBytes) + "\r\n"
    + "--" + boundary + "\r\nContent-Disposition: form-data; name=\"from\"\r\n\r\nmp3\r\n"
    + "--" + boundary + "\r\nContent-Disposition: form-data; name=\"to\"\r\n\r\nm4a\r\n"
    + "--" + boundary + "--";

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
    .uri(URI.create("https://filechanger.io/api/convert"))
    .header("X-Api-Key", "fc_your_api_key_here")
    .header("Content-Type", "multipart/form-data; boundary=" + boundary)
    .POST(BodyPublishers.ofString(body))
    .build();

HttpResponse<byte[]> response = client.send(
    request, BodyHandlers.ofByteArray());
java.nio.file.Files.write(Path.of("output.m4a"), response.body());

import Network.HTTP.Client
import Network.HTTP.Client.MultipartFormData
import qualified Data.ByteString.Lazy as BL

main :: IO ()
main = do
  manager <- newManager defaultManagerSettings
  initialReq <- parseRequest "POST https://filechanger.io/api/convert"
  let req = initialReq
        { requestHeaders = [("X-Api-Key", "fc_your_api_key_here")] }
  request <- formDataBody
    [ partFileSource "file" "input.mp3"
    , partBS "from" "mp3"
    , partBS "to" "m4a"
    ] req

  response <- httpLbs request manager
  BL.writeFile "output.m4a" (responseBody response)

About MP3

MP3 (MPEG-1 Audio Layer III) is the format that made digital music portable and remains the most universally playable audio there is. Its psychoacoustic lossy compression throws away the detail the ear cannot hear to shrink files dramatically, and every phone, browser, car stereo, and media player of the last twenty-five years can play the result.

About M4A

M4A is AAC audio in an MP4 container, the format iTunes, Apple Music, and the iPhone's Voice Memos all produce. It sounds noticeably better than MP3 at the same bitrate and carries chapters, cover art, and metadata, which is why podcasts and audiobooks are distributed in it.

Frequently asked questions

How do I convert MP3 to M4A?

Upload your file in the browser converter and pick M4A as the target, or POST it to /api/convert with from=mp3 and to=m4a. The response body is the converted file.

Is converting MP3 to M4A free?

Yes. Every account gets 200 MB of conversions free, metered on input size. After that you pay only for what you convert, from $0.10 per GB, with no monthly fee. See pricing for the paid tiers.

Is there an API for MP3 to M4A conversion?

Yes, this whole conversion is one POST to /api/convert (the code examples above show it in five languages), plus an MCP server so AI agents can run it directly.

Does converting MP3 to M4A improve the audio quality?

No, and nothing can. MP3 encoding permanently discards part of the signal, so every later copy starts from what survived. Converting to M4A preserves that as faithfully as M4A allows, but it cannot restore detail the encoder threw away. What you gain is a file in the shape the rest of your toolchain wants.