Convert Kindle (AZW3) to EPUB

Turn Kindle (AZW3), Amazon's KF8 Kindle format used by modern Kindle devices, into EPUB, the standard e-book format for e-readers and reading apps. FileChanger runs the document 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=azw3 and to=epub, 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.

Convert Kindle (AZW3) to EPUB 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.azw3" \
  -F "from=azw3" \
  -F "to=epub" \
  -o output.epub

import requests

with open("input.azw3", "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": "azw3", "to": "epub"},
    )

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

const formData = new FormData();
formData.append("file", fileInput.files[0]);
formData.append("from", "azw3");
formData.append("to", "epub");

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.azw3"));

String body = "--" + boundary + "\r\n"
    + "Content-Disposition: form-data; name=\"file\"; filename=\"input.azw3\"\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\nazw3\r\n"
    + "--" + boundary + "\r\nContent-Disposition: form-data; name=\"to\"\r\n\r\nepub\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.epub"), 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.azw3"
    , partBS "from" "azw3"
    , partBS "to" "epub"
    ] req

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

About EPUB

EPUB is the open standard e-book format used by virtually every e-reader and reading app outside the Kindle ecosystem. It packages reflowable HTML content with metadata, making it the distribution format of choice for publishers and self-published authors alike.

Frequently asked questions

How do I convert Kindle (AZW3) to EPUB?

Upload your file in the browser converter and pick EPUB as the target, or POST it to /api/convert with from=azw3 and to=epub. The response body is the converted file.

Is converting Kindle (AZW3) to EPUB free?

Yes. The free tier includes 2 GB of conversions per month, metered on input size. See pricing for the paid tiers.

Is there an API for Kindle (AZW3) to EPUB 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.