Voices, programmatically.

Plans

Monthly subscription, billed by Stripe. Quota resets each billing cycle. Cancel anytime from the billing portal.

Your API key is shown once right after checkout — store it somewhere safe, and never ship it in front-end code.

Documentation

Base URL: — authenticate every request with an X-API-Key header.

Converts text to speech. Returns raw MP3 bytes in the response body. Response headers report X-Chars-Used, X-Chars-Remaining, and X-Plan.

# curl
curl -X POST "$BASE/api/v1/tts" \
  -H "X-API-Key: nl_api_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"text":"Hello from Nudge Laboratories","voice":"en-US-AriaNeural","rate":0,"pitch":0}' \
  --output speech.mp3

# Python
import requests

r = requests.post(
    f"{BASE}/api/v1/tts",
    headers={"X-API-Key": "nl_api_YOUR_KEY"},
    json={"text": "Hello from Nudge Laboratories", "voice": "en-US-AriaNeural"},
)
if r.ok:
    open("speech.mp3", "wb").write(r.content)
    print("remaining:", r.headers["X-Chars-Remaining"])

<?php // PHP
$ch = curl_init($base . "/api/v1/tts");
curl_setopt_array($ch, [
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_POST => true,
  CURLOPT_POSTFIELDS => json_encode(["text" => "Hello from Nudge Laboratories", "voice" => "en-US-AriaNeural"]),
  CURLOPT_HTTPHEADER => ["X-API-Key: nl_api_YOUR_KEY", "Content-Type: application/json"],
]);
$audio = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) === 200) file_put_contents("speech.mp3", $audio);

Lists every available voice with its voice_id, locale, and gender. Use the voice_id in TTS requests.

Returns your plan, billing cycle end date, and remaining character quota — poll it before large jobs.

{
  "success": true,
  "account": { "plan": "api_pro", "billing_cycle_end": "2026-08-06T…" },
  "quota": { "chars_limit": 50000000, "chars_used": 120450, "chars_remaining": 49879550 }
}

401 missing/invalid key · 402 quota exceeded · 400 bad request · 502 engine error. All errors return JSON with a detail field.