August 17, 2020

Paytm payments for serverless websites

Sambit Sahoo

Paytm-Netlify-Lambda πŸš€

Paytm payments integration for serverless JAMstack websites using Netlify lambda functions. This repo will save you from the nightmare of setting up a serverless payment integration from scratch.

πŸš€ It’s live here

πŸ’₯ GitHub repo is here

πŸ“‘ Table of Contents

  • πŸ”° [Getting Started
  • πŸ“ Setup
    • 🌱 Basic Setup
    • πŸ”₯ Usage with Firebase
  • πŸ—œ Integration
  • πŸ““ Notes
    • πŸ€“ How it Works ?
    • πŸŒ‹ Errors
    • πŸ“” References

Getting Started

To get started clone this repo.

git clone [email protected]:soulsam480/paytm-netlify-lambda.git

cd paytm-netlify-lambda

npm install

To serve the lambda functions locally we can run

npm run start

But before that we have to setup the functions otherwise there will be errors!!


Open the repo in your favorite text-editor and the file structure will be like this

  • config
  • dist
  • src
    • cred
    • paytm
      • checksum.js
      • crypt.js
      • paytm_config.js
      • paytmChecksum.js
    • payConf.js
    • payment.js

Webpack cofig sits inside the config folder. All our functions will be build into the dist folder. So it’s good if we don’t touch that folder.

Basic Setup

Open paytm_config.js inside the paytm folder.

module.exports = {
  paytm_config: {
    PAYTM_ENVIRONMENT: "TEST", //possible values:  TEST | PROD
    MID: " Your MID", // Get it From use Test id for test purpose and Production id for Production Purpose
    WEBSITE: "WEBSTAGING", // USE WEBSTAGING for testing, You Will get it for Production here
    CHANNEL_ID: "WEB", // Use WEB for Desktop Website and WAP for Mobile Website
    INDUSTRY_TYPE_ID: "Retail", // Use Retail for Testing, For Production You Can Get it from here
    MERCHANT_KEY: " Your MERCHANT_KEY", // Get it From use Test key for test purpose and Production key for Production Purpose
      "", // Modify and Use this url for verifying payment

Change the MID and Merchant Key to your paytm merchant account. The callback url will be updated after you have deployed these functions to netlify. So we will leave it as it is. Again if you wish to change the parameters for production build, the respective fields will be changed with the production credentials.

If you don’t wish to use firebase for order validation and confirmation, you can stop here and remove firebase completely from the project. If you wish to use, let’s move in to the next step.

Usage with Firebase

We will use firebase-admin sdk for nodejs to access admin privilages. With firebase admin running on server we can perform CRUD operations on realtime database easily.

To setup admin sdk you need a firebase service account. To get yourself one open you firebase admin dashboard and then project settings > service accounts. Create one for your project and download the credentials in json. Then open src/cred/authKey.js . Add the credentials in their respective places.

module.exports = {
  authKey: {
    type: "service_account",
    project_id: "Your Project id",
    private_key_id: " Your PRIVATE_KEY_ID",
    private_key: "Your PRIVATE_KEY"
    client_email: "Your client email",
    client_id: "Your client id",
    auth_uri: "your auth uri",
    token_uri: "auth token uri",
    auth_provider_x509_cert_url: "cert url provider",
    client_x509_cert_url: " your CERT_URL",

Then open src/payConf.js and add your database URL. With this the setup is complete.

After each successful payment firebase-admin will create an order inside

Orders/dd_mm_yy(current date)/orderId

this could be further used to verify an proceed with the payment. This is the only advantage of using firebase inside this project. If you don’t wish to verify your orders, you can drop firebase completely and move on with the basic approach.

As the setup is complete you can deploy this project to netlify by pushing the code into an it repo. The instruction on how to deploy from a git repo is here

There are two methods to integrate these functions to your project.


This method makes a POST request to the api and creates and submits the form clent-side in browser. Let’s move further for a good explanation.

To make API calls you have to pass these parameters inside the body of your post request. Here is an example using axios.

        method: "post",
        data: {
          amount: payment amount, //must be an integer Mandatory
          name: "customer_name", // _ is space allowed inbetween. ex. Sambit_sahoo
          email: "customer_email", //valid customer email
          orderid: "Order_id", // space allowed inbetween ex. OD123231 or OD_12324
          mobile: "customer_mobileno",
        headers: {
          "Content-Type": "application/json",
        .then(async (res) => {
          const params =;
          params["CHECKSUMHASH"] =;
          //Here the helper function post.js creates the from api response and submits.
            target: "_self",
            params: params,
        .catch((err) => {

Here is the helper function which creates and submits the form client side inside browser.

//This plugin is used to perform form action request from jsvascript.
//This is derived from
function isDate(val) {
  // Cross realm comptatible
  return === "[object Date]";

function isObj(val) {
  return typeof val === "object";

export function stringifyValue(val) {
  if (isObj(val) && !isDate(val)) {
    return JSON.stringify(val);
  } else {
    return val;

function buildForm({ action, target, params }) {
  const form = document.createElement("form");
  form.setAttribute("method", "post");
  form.setAttribute("action", action);
  form.setAttribute("target", target);

  Object.keys(params).forEach((key) => {
    const input = document.createElement("input");
    input.setAttribute("type", "hidden");
    input.setAttribute("name", key);
    input.setAttribute("value", stringifyValue(params[key]));

  return form;

export default function post(details) {
  const form = buildForm(details);

Again after a successful payment you will be redirected to the page sent from the payment confirmation function i.e. payConf.js.

To change your response URLs go to line 89 for payment success URL, line 93 and 96 for Failure URL.


This project is an wrapper and improvement over the project created by Satyam. You can find the github repo here. He implemented this approach using firebase cloud functions.

How it Works

Netlify functions are AWS lambda functions which return a callback for an API request. I originally intended to implement this approach without experess.js. But I ran into many errors and couldn’t figure a way out. So i went with the Express way πŸ˜‚.

When you hit the payment endpoint with the data inside a POST request, it generates a checksum for the provided orderid using paytm’s generate checksum logic. After successful generation it responds with the credentials for the payment page. The response from the promise by axios is used to create the HTML form by the elper function post.js and submitted immediately.

After Successful payment, your callback function which is src/payConf.js verifies the status of the transaction from paytm transaction status api through an unique signature. after successful verification, the callback function creates an order on your firebase database and responds with your payment succes page url.


I have handled most of the errors 😌. Still there is always a bug πŸ›. If you ran into any issues try using console.log() to find and fix the error by using google. If you don’t find any way reach me here. I’ll be happy to help πŸ‘πŸΌπŸ‘πŸΌ !!


Links to some of the resources that helped me create this project.

I’m not good at writing documentations. So if i missed something and you ran into an unknown issue please reach me on

mail πŸ“§ / twitter πŸ•Š / instagram πŸ–Ό

Thank You! ✌🏼