NextMSG API Docs

GET/v1/instances

token: wa_live_your_token

GET/v1/instances/:instanceId/status

token: wa_live_your_token

POST/{INSTANCE_ID}/messages/chat

Content-Type: application/x-www-form-urlencoded

 token=wa_live_your_token&to=254712345678&body=Hello from client system

import requests

base_url = "http://localhost:3000"
instance_id = "wacc_your_instance_id"
url = f"{base_url}/{instance_id}/messages/chat"

response = requests.post(
    url,
    data={
        "token": "wa_live_your_token",
        "to": "254712345678",
        "body": "Hello from Python"
    },
    timeout=30,
)

print(response.status_code)
print(response.text)

const baseUrl = "http://localhost:3000";
const instanceId = "wacc_your_instance_id";

const payload = new URLSearchParams({
  token: "wa_live_your_token",
  to: "254712345678",
  body: "Hello from JavaScript/TypeScript"
});

const res = await fetch(`${baseUrl}/${instanceId}/messages/chat`, {
  method: "POST",
  headers: { "Content-Type": "application/x-www-form-urlencoded" },
  body: payload.toString()
});

console.log(res.status, await res.text());

using System.Net.Http;

using var client = new HttpClient();
using var form = new FormUrlEncodedContent(new Dictionary<string, string>
{
    ["token"] = "wa_live_your_token",
    ["to"] = "254712345678",
    ["body"] = "Hello from .NET"
});

var response = await client.PostAsync(
    "http://localhost:3000/wacc_your_instance_id/messages/chat",
    form
);

Console.WriteLine((int)response.StatusCode);
Console.WriteLine(await response.Content.ReadAsStringAsync());

GET/v1/messages/inbound

token: wa_live_your_token

Optional query params:
instanceId=wacc_your_instance_id
limit=50

const res = await fetch("http://localhost:3000/v1/messages/inbound?limit=50", {
  headers: { token: "wa_live_your_token" }
});

const data = await res.json();
console.log(data.messages);

Configure the webhook URL from the dashboard. When a connected WhatsApp instance receives a message, NextMSG stores it and sends a JSON POST to your URL.

POST https://yourserver.com/whatsapp/webhook
Content-Type: application/json
X-NextMSG-Event: message.received
X-NextMSG-Signature: sha256=<hmac_sha256_body_signature>

{
  "event": "message.received",
  "tenantId": "tenant_...",
  "accountId": "wacc_...",
  "message": {
    "id": "inmsg_...",
    "from": "252612345678",
    "to": "252600000000",
    "type": "chat",
    "body": "Hello",
    "externalId": "...",
    "hasMedia": false,
    "receivedAt": "2026-06-28T12:00:00.000Z"
  }
}

import crypto from "node:crypto";

function verifyNextMsgWebhook(rawBody, signatureHeader, secret) {
  const expected = "sha256=" + crypto
    .createHmac("sha256", secret)
    .update(rawBody)
    .digest("hex");

  const actual = Buffer.from(signatureHeader || "");
  const wanted = Buffer.from(expected);
  return actual.length === wanted.length && crypto.timingSafeEqual(actual, wanted);
}

POST/{INSTANCE_ID}/messages/document

Content-Type: multipart/form-data

 token=wa_live_your_token
 to=254712345678
 caption=Monthly invoice attached
 document=@invoice.pdf

import requests

base_url = "http://localhost:3000"
instance_id = "wacc_your_instance_id"
url = f"{base_url}/{instance_id}/messages/document"

with open("invoice.pdf", "rb") as f:
    response = requests.post(
        url,
        data={
            "token": "wa_live_your_token",
            "to": "254712345678",
            "caption": "Monthly invoice attached",
        },
        files={"document": ("invoice.pdf", f, "application/pdf")},
        timeout=60,
    )

print(response.status_code)
print(response.text)

import fs from "node:fs";

const baseUrl = "http://localhost:3000";
const instanceId = "wacc_your_instance_id";

const form = new FormData();
form.append("token", "wa_live_your_token");
form.append("to", "254712345678");
form.append("caption", "Monthly invoice attached");
form.append(
  "document",
  new Blob([fs.readFileSync("invoice.pdf")], { type: "application/pdf" }),
  "invoice.pdf"
);

const res = await fetch(`${baseUrl}/${instanceId}/messages/document`, {
  method: "POST",
  body: form
});

console.log(res.status, await res.text());

package main

import (
  "bytes"
  "io"
  "mime/multipart"
  "net/http"
  "os"
)

func main() {
  var body bytes.Buffer
  writer := multipart.NewWriter(&body)

  _ = writer.WriteField("token", "wa_live_your_token")
  _ = writer.WriteField("to", "254712345678")
  _ = writer.WriteField("caption", "Monthly invoice attached")

  part, _ := writer.CreateFormFile("document", "invoice.pdf")
  file, _ := os.Open("invoice.pdf")
  defer file.Close()
  _, _ = io.Copy(part, file)
  _ = writer.Close()

  req, _ := http.NewRequest(
    http.MethodPost,
    "http://localhost:3000/wacc_your_instance_id/messages/document",
    &body,
  )
  req.Header.Set("Content-Type", writer.FormDataContentType())

  resp, _ := http.DefaultClient.Do(req)
  defer resp.Body.Close()
  b, _ := io.ReadAll(resp.Body)
  println(resp.StatusCode, string(b))
}