Veifying webhooks with the Svix libraries

First install the libraries if you haven't already:

JavaScript

npm install svix
// Or
yarn add svix

Python

Rust

Go

Java

Kotlin

Ruby

C#

PHP

CLI

cURL

Then verify webhooks using the code below. The payload is the raw (string) body of the request, and the headers are the headers passed in the request.

USE THE RAW REQUEST BODY

You need to use the raw request body when verifying webhooks, as the cryptographic signature is sensitive to even the slightest changes. You should watch out for frameworks that parse the request as JSON and then stringify it because this too will break the signature verification.

Framework specific examples

Here are examples on how to adjust the above examples to your favourite framework.

Python (Django)

from django.http import HttpResponse

from svix.webhooks import Webhook, WebhookVerificationError

secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw"

@csrf_exempt
def webhook_handler(request):
    headers = request.headers
    payload = request.body

    try:
        wh = Webhook(secret)
        msg = wh.verify(payload, headers)
    except WebhookVerificationError as e:
        return HttpResponse(status=400)

    # Do something with the message...

    return HttpResponse(status=204)

Python (Flask)

from flask import request

from svix.webhooks import Webhook, WebhookVerificationError

secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw"

@app.route('/webhook/')
def webhook_handler():
    headers = request.headers
    payload = request.get_data()

    try:
        wh = Webhook(secret)
        msg = wh.verify(payload, headers)
    except WebhookVerificationError as e:
        return ('', 400)

    # Do something with the message...

    return ('', 204)

Python (FastAPI)

from fastapi import Request, Response, status

from svix.webhooks import Webhook, WebhookVerificationError

secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw"

@router.post("/webhook/", status_code=status.HTTP_204_NO_CONTENT)
async def webhook_handler(request: Request, response: Response):
    headers = request.headers
    payload = await request.body()

    try:
        wh = Webhook(secret)
        msg = wh.verify(payload, headers)
    except WebhookVerificationError as e:
        response.status_code = status.HTTP_400_BAD_REQUEST
        return

    # Do something with the message...

Node.js (Next.js)

The svix-example repo contains an example of how to verify and use webhooks in a Next.js application.

import { Webhook } from "svix";
import { buffer } from "micro";

export const config = {
    api: {
        bodyParser: false,
    },
}

const secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw";

export default async function handler(req, res) {
    const payload = (await buffer(req)).toString();
    const headers = req.headers;

    const wh = new Webhook(secret);
    let msg;
    try {
        msg = wh.verify(payload, headers);
    } catch (err) {
        res.status(400).json({});
    }

    // Do something with the message...

    res.json({});
}

Node.js (Next.js 13 App Router)

import { Webhook } from "svix";

const webhookSecret: string = process.env.WEBHOOK_SECRET || "your-secret";

export async function POST(req: Request) {
  const svix_id = req.headers.get("svix-id") ?? "";
  const svix_timestamp = req.headers.get("svix-timestamp") ?? "";
  const svix_signature = req.headers.get("svix-signature") ?? "";

  const body = await req.text();

  const sivx = new Webhook(webhookSecret);

  let msg;

  try {
    msg = sivx.verify(body, {
      "svix-id": svix_id,
      "svix-timestamp": svix_timestamp,
      "svix-signature": svix_signature,
    });
  } catch (err) {
    return new Response("Bad Request", { status: 400 });
  }

  console.log(msg);

  // Rest

  return new Response("OK", { status: 200 });
}

Node.js (Netlify Functions)

import { Webhook } from "svix";

const secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw";


export const handler = async ({body, headers}) => {
    const payload = body;

    const wh = new Webhook(secret);
    let msg;
    try {
        msg = wh.verify(payload, headers);
    } catch (err) {
        res.status(400).json({});
    }

    // Do something with the message...

    res.json({});
}

Node.js (Express)

Note: When integrating this example into a larger codebase, you will have to make sure not to apply the express.json() middleware to the webhook route, because the payload has to be passed to wh.verify without any prior parsing.

import { Webhook } from "svix";
import bodyParser from "body-parser";

const secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw";

app.post('/webhook', bodyParser.raw({ type: 'application/json' }), (req, res) => {
    const payload = req.body;
    const headers = req.headers;

    const wh = new Webhook(secret);
    let msg;
    try {
        msg = wh.verify(payload, headers);
    } catch (err) {
        res.status(400).json({});
    }

    // Do something with the message...

    res.json({});
});

Node.js (NestJS)

Initialize the application with the rawBody flag set to true. See the (NestJS docs)[https://docs.nestjs.com/faq/raw-body#raw-body] for details.

// main.ts
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(
    AppModule,
    { rawBody: true } // add rawBody flag
  );
  await app.listen(3000);
}
bootstrap();

// webhook.controller.ts
import { Controller, Post, RawBodyRequest, Req } from '@nestjs/common';
import { Request } from 'express';
import { Webhook } from 'svix';

@Controller('webhook')
class WebhookController {
  @Post()
  webhook(@Req() request: RawBodyRequest<Request>) {
    const secret = 'whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw';
    const wh = new Webhook(secret);

    const payload = request.rawBody.toString('utf8');
    const headers = request.headers;

    let msg;
    try {
      msg = wh.verify(payload, headers);
    } catch (err) {
      // handle error
    }

    // Do something with the message...
  }
}

Node.js (Nuxt)

import { Webhook } from "svix";

const secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw";

export default defineEventHandler(async (event) => {
  const headers = getRequestHeaders(event);
  const payload = await readRawBody(event);

  const wh = new Webhook(secret);

  let msg;

  try {
      msg = wh.verify(payload, headers);
  } catch (err) {
      setResponseStatus(event, 400);
      return "Bad Request";
  }

  // Do something with the message...
  return "OK";
})

Go (Standard lib)

package main

import (
	"io"
	"log"
	"net/http"

	svix "github.com/svix/svix-webhooks/go"
)

const secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw"

func main() {

	wh, err := svix.NewWebhook(secret)
	if err != nil {
		log.Fatal(err)
	}

	http.HandleFunc("/webhook", func(w http.ResponseWriter, r *http.Request) {
		headers := r.Header
		payload, err := io.ReadAll(r.Body)
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		err = wh.Verify(payload, headers)
		if err != nil {
			w.WriteHeader(http.StatusBadRequest)
			return
		}

		// Do something with the message...

		w.WriteHeader(http.StatusNoContent)

	})
	http.ListenAndServe(":8080", nil)
}

Go (Gin)

package main

import (
	"io"
	"log"
	"net/http"

	"github.com/gin-gonic/gin"
	svix "github.com/svix/svix-webhooks/go"
)

const secret = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw"

func main() {

	wh, err := svix.NewWebhook(secret)
	if err != nil {
		log.Fatal(err)
	}

	r := gin.Default()
	r.POST("/webhook", func(c *gin.Context) {
		headers := c.Request.Header
		payload, err := io.ReadAll(c.Request.Body)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}

		err = wh.Verify(payload, headers)
		if err != nil {
			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
			return
		}

		// Do something with the message...

		c.JSON(200, gin.H{})
	})
	r.Run()
}

Rust (axum)

Add the webhook_in route below to an axum router.

use axum::{body::Bytes, http::StatusCode};
use hyper::HeaderMap;

pub const SECRET: &'static str = "whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw";

pub async fn webhook_in(headers: HeaderMap, body: Bytes) -> StatusCode {
    let Ok(wh) = svix::webhooks::Webhook::new(SECRET) else {
        return StatusCode::INTERNAL_SERVER_ERROR;
    };

    if let Err(_) = wh.verify(&body, &headers) {
        return StatusCode::BAD_REQUEST;
    }

    // Do something with the message...

    StatusCode::NO_CONTENT
}

Ruby (Ruby on Rails)

Once you've set up your project add a route to your config/routes.rb file at the top of the Rails.application.routes.draw block:

Rails.application.routes.draw do
  post "/webhook", to: "webhook#index"

  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
end

The route above declares that POST /webhook requests are mapped to the index action of WebhookController.

To create WebhookController and its index action, we'll run the controller generator (with the --skip-routes option because we already have an appropriate route):

bin/rails generate controller Webhook index --skip-routes

Rails will create several files for you:

    create  app/controllers/webhook_controller.rb
    invoke  erb
    create    app/views/webhook
    create    app/views/webhook/index.html.erb
    invoke  test_unit
    create    test/controllers/webhook_controller_test.rb
    invoke  helper
    create    app/helpers/webhook_helper.rb
    invoke    test_unit
    invoke  assets
    invoke    scss
    create      app/assets/stylesheets/webhook.scss

Now we can add our verification logic to the newly created app/controllers/webhook_controller.rb file:

require 'svix'

class WebhookController < ApplicationController
  protect_from_forgery with: :null_session # disables CSRF middleware; required for API endpoints

  def index
    begin
      payload = request.body.read
      headers = request.headers
      wh = Svix::Webhook.new("whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw")

      json = wh.verify(payload, headers)

      # Do something with the message...

      head :no_content
    rescue
      head :bad_request
    end
  end
end

PHP (Laravel)

In your routes/api.php file add the following after the last use directive:

use Svix\Webhook;
use Svix\Exception\WebhookVerificationException;

Route::post('webhook', function(Request $request) {
    $payload = $request->getContent();
    $headers = collect($request->headers->all())->transform(function ($item) {
        return $item[0];
    });

    try {
        $wh = new Webhook("whsec_MfKQ9r8GKYqrTwjUPD8ILPZIo2LaLaSw");
        $json = $wh->verify($payload, $headers);

        # Do something with the message...

        return response()->noContent();
    } catch (WebhookVerificationException $e) {
        return response(null, 400);
    }
});