Watermark API

Overview

The API embeds an inaudible, recipient-unique signature into an audio file, and later identifies which signature a leaked file carries. Use it to sign promos before they go out, or to check a file that turned up somewhere it shouldn't.

• Base URL: https://listeningcopy.com
• All requests use HTTPS. Files are sent as multipart/form-data.
• Watermarked output is always MP3 320. A signed file is a listening copy, not a master.
• Files are processed in memory and not retained. Only the signature id and your label are stored, so trace can name a match.

Authentication

Create a key in the Developers console. Send it as a bearer token on every request. Keep it secret; it spends your credits.

Authorization: Bearer lc_live_xxxxxxxxxxxxxxxxxxxxxxxx

A missing or invalid key returns 401. Revoke a key any time in the console.

Credits & limits

Each watermark and each trace costs 1 credit. Your plan's monthly allowance is spent first, then purchased credits (which never expire). When you run out, calls return 402 and we email you a heads-up before that happens.

Check your balance any time with GET /v1/account. Keep uploads under 2 GB.

Watermark a file

POST /v1/watermark

Upload an audio file and a label identifying the recipient. Returns the signed MP3 and the signature id.

The response body is the MP3. The signature id comes back in the X-Watermark-Id header, store it if you want to look it up later.

curl -X POST https://listeningcopy.com/v1/watermark \
  -H "Authorization: Bearer lc_live_..." \
  -F "file=@mix.wav" \
  -F "label=Jane Doe, radio promo" \
  -o watermarked.mp3 -D -

Trace a file

POST /v1/trace

Upload a suspect file. If it carries one of your signatures, you get back the id and the label it was signed with. Add ?deep=1 for a slower, more robust scan that recovers signatures from heavily degraded files.

curl -X POST https://listeningcopy.com/v1/trace \
  -H "Authorization: Bearer lc_live_..." \
  -F "file=@leaked.mp3"

Response:

{
  "matched": true,
  "results": [
    { "id": "a4f5ecf5a5918a644435c6b0f89c0f5a",
      "label": "Jane Doe, radio promo",
      "watermarkedAt": 1784923715799 }
  ]
}

No match returns { "matched": false, "results": [] }. A trace still costs 1 credit whether or not it matches.

Account

GET /v1/account

Your current credit balance and total watermarks.

curl https://listeningcopy.com/v1/account -H "Authorization: Bearer lc_live_..."
# { "credits": 380, "watermarked": 214 }

Errors

Examples

Node

import { readFileSync } from "node:fs";

const form = new FormData();
form.set("file", new Blob([readFileSync("mix.wav")]), "mix.wav");
form.set("label", "Jane Doe, radio promo");

const res = await fetch("https://listeningcopy.com/v1/watermark", {
  method: "POST",
  headers: { Authorization: "Bearer lc_live_..." },
  body: form,
});
const id = res.headers.get("X-Watermark-Id");
const mp3 = Buffer.from(await res.arrayBuffer());

Python

import requests

with open("mix.wav", "rb") as f:
    r = requests.post(
        "https://listeningcopy.com/v1/watermark",
        headers={"Authorization": "Bearer lc_live_..."},
        files={"file": f},
        data={"label": "Jane Doe, radio promo"},
    )
open("watermarked.mp3", "wb").write(r.content)
print(r.headers["X-Watermark-Id"])