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Step-by-Step Guide: Replacing Google Optimize With Vercel Edge Functions

March 7, 2024 by Daria Andrieieva
  • User Experience
vercel edge functions

In the ever-evolving world of web development, optimization, and performance enhancement are top priorities for any website owner. Google Optimize has been a popular choice for A/B testing and optimization, but many are now turning to Vercel Edge Functions as a powerful alternative. 

This transition offers a more efficient, cost-effective, and performance-driven approach to website optimization. Join Kapsys as we explore Vercel and how to replace Google Optimize with Vercel Edge Functions for better results.



What is Vercel?

Before we delve into the process of replacing Google Optimize with Vercel Edge Functions, let's start with an overview of Vercel itself.


Vercel is a cloud platform for frontend development that provides hosting, continuous deployment, and serverless functions. It allows developers to build and deploy websites and web applications with ease. The core features of Vercel include:

  • Effortless Deployment: Vercel simplifies the deployment process, making it easy for developers to push their code and see it live in seconds.

  • Global Content Delivery: Vercel offers a global content delivery network (CDN) to ensure fast and reliable content delivery to users worldwide.

  • Serverless Functions: Vercel's serverless functions enable you to run code on the edge, bringing your applications closer to your users for improved performance.


  • Continuous Integration/Continuous Deployment (CI/CD): Vercel automates the CI/CD process, making it convenient for developers to maintain and update their projects.

Now that we understand Vercel let's explore why Vercel Edge Functions is a suitable replacement for Google Optimize.

Read: Vercel vs. Traditional Hosting: Pros And Cons

Why Replace Google Optimize with Vercel Edge Functions?

Google Optimize has been a reliable tool for A/B testing and web optimization, but it does have some limitations that Vercel Edge Functions can address effectively.

  • Performance: Vercel's global edge network ensures that your website's content is served from the nearest data center to the user. This minimizes latency and significantly improves page load times.

  • Reduced Third-Party Dependencies: Google Optimize often requires additional JavaScript tags, which can slow down your website. Vercel Edge Functions allow you to run serverless code directly at the edge, reducing the need for third-party dependencies.

  • Simplified Configuration: Vercel's intuitive interface and robust documentation make it easy to configure A/B tests, deploy changes, and monitor performance without complex setups.

  • Cost Efficiency: While Google Optimize comes with a price tag, Vercel offers free plans and competitive pricing, making it a more cost-effective solution.

Now that we understand the advantages of replacing Google Optimize with Vercel Edge Functions let's delve into the steps required to make this transition.

Read: Tips For A Faster Website Optimizing Vercel Speed

google optimize replacement

Replacing Google Optimize with Vercel Edge Functions

Let's break this down into simple steps: 

Step 1. Setting up a Vercel account

Getting started with Vercel Edge Functions is easy and cost-effective. Follow these steps to set up your Vercel account:

  • Visit the Vercel website and click on the "Sign Up" button.

  • You can sign up using your GitHub, GitLab, or email. Choose the method that suits you best.

  • Vercel offers free plans, so you can start experimenting without incurring costs. You only pay when you need more advanced features or higher usage limits.

Step 2. Project creation

Once you've created your Vercel account, it's time to set up a project for your website:

  • Log in to your Vercel account.

  • Click on the "Create" button to start a new project.

Vercel will guide you through the project creation process. You'll be prompted to link your project to a Git repository. This connection makes deploying your website a breeze.

Step 3. Deploy your website

Vercel's integration with Git repositories, such as GitHubGitLab, and Bitbucket, simplifies the deployment process:

  • After linking your project to a Git repository, Vercel will automatically detect changes in your codebase.

  • With every push to your repository, Vercel will initiate an automatic deployment. This ensures your website is always up-to-date with your latest changes.

To deploy your website using Vercel and Vercel Edge Functions, you only need to focus on your code and let the platform handle the rest.

Step 4. Creating A/B tests with Vercel Edge Functions

Now, let's dive into the heart of the matter: creating A/B tests and optimization experiments using Vercel Edge Functions.

Writing your function

To create an A/B test, you'll write a serverless function in JavaScript or TypeScript. This function will serve as your A/B test, containing the variations you want to test. Here's an example of a simple A/B test function written in JavaScript:

// abTest.js
module.exports = (request) => {
  // Define the variations
  const variations = ['A', 'B'];
  // Randomly select a variation
  const selectedVariation = variations[Math.floor(Math.random() * variations.length)];

  // Return the selected variation
  return new Response(selectedVariation, {
    status: 200,
    headers: { 'Content-Type': 'text/plain' },

In this example, the function randomly selects between variations 'A' and 'B' and returns the selected deviation as the response.

Deploying the function

To deploy your A/B test function to Vercel Edge Functions, follow these steps:

  1. Open your Vercel dashboard.

  2. Click on your project where you want to deploy the A/B test function.

  3. Navigate to the "Functions" section.

  4. Click the "Add" button to create a new function and upload your JavaScript file.

Setting up routing

Now, you need to configure routing rules to determine which users see which variation. Vercel Edge Functions makes this process straightforward:

  1. In your Vercel dashboard, select your project.

  2. Go to the "Routing" section.

  3. Add a new route that specifies the path where you want to apply your A/B test function. For example, if you want to apply the A/B test to the path "/homepage," create a route that matches this path.

  4. In the route settings, assign your A/B test function as the "Response" for this route.

Monitoring and analyzing

Use Vercel's built-in analytics tools to track the performance of your A/B tests. You can assess user engagement, conversion rates, and other relevant metrics directly from your Vercel dashboard.

Read: How To Personalize Website URL with Vercel?

Step 5. Custom domain configuration

Suppose you've been using a custom domain with Google Optimize. In that case, you can easily configure it with Vercel Edge Functions to maintain your brand identity and provide a seamless transition for your users. Here's how:

  1. In your Vercel dashboard, go to the project settings.

  2. Under the "Domains" section, click "Add or transfer a domain."

  3. Follow the steps to add your custom domain. You may need to update DNS records or configure your domain registrar settings to point to Vercel.

Once your custom domain is configured, your users will continue to access your website using the same domain as before.

Step 6. Performance optimization with Edge Config

Now, let's explore how Edge Config can help fine-tune your website's performance with Vercel's global network.

Edge routing

Configure how requests are routed through Vercel's edge network to optimize content delivery for your users. This is done through the Vercel dashboard:

  1. In your project settings, navigate to the "Edge" section.

  2. Create routing rules that specify how different types of content are handled at the edge.

For instance, you can route images through a content delivery network (CDN) for faster delivery while routing dynamic content to specific serverless functions for processing.

Edge handlers

Implement custom logic at the edge for advanced optimizations and personalizations. Here's an example of a simple edge handler that adds a custom header to every response:

// edgeHandler.js
addEventListener('fetch', (event) => {

async function handleRequest(request) {
  const response = await fetch(request);

  // Add a custom header to the response
  response.headers.set('X-Custom-Header', 'Hello from the edge!');

  return response;

HTTP headers

Set HTTP headers at the edge to ensure the proper security and cache policies for your site. You can add or modify headers using edge handlers, as demonstrated above.

Fallback pages

Define custom fallback pages to improve error handling and user experience. For example, you can set up a custom 404 error page to guide users when they land on a non-existent URL.

By leveraging Edge Config, you can maximize the performance benefits of Vercel's Edge Functions and tailor your website's delivery precisely to your needs.

Read: How to Add Vercel Environment Variables To Your Project


Vercel's Edge Functions empower developers to optimize their web applications by executing code at the network's edge. While this provides immense benefits, it's common to encounter issues during development and deployment.

Identifying common issues

Before diving into the solutions, let's look at some typical problems you might encounter when working with Vercel Edge Functions:

  • Deployment Failures: Functions failing to deploy, resulting in 404 errors or other issues.

  • Slow Response Times: Slow performance due to inefficient code or complex routing configurations.

  • CORS Errors: Cross-Origin Resource Sharing (CORS) issues that prevent your functions from executing.

  • Authentication Problems: Difficulty in authenticating requests and securing your roles.

  • Runtime Errors: Code errors that cause parts to crash or produce incorrect results.

Troubleshooting Strategies

Here are some strategies that can help you with Vercel Edge Functions  troubleshooting: 

Check your code

Start by reviewing your code thoroughly. Ensure it is free of syntax errors, logical issues, or runtime exceptions. Pay special attention to your function's entry point, handling of requests, and error handling.

Deployment logs

Inspect the deployment logs provided by Vercel. These logs often contain valuable information about the deployment process, potential errors, or issues related to your functions.

Configuration review

Double-check your routing and configuration settings, ensuring they match your project's requirements. Mistakes in routing can lead to unexpected behavior.

CORS settings

While implementing Vercel Edge Functions, if you encounter CORS issues, ensure your CORS settings are correctly configured. Allow or restrict specific domains based on your application's needs.

Response times

Monitor the response times of your function and optimize code as necessary. Utilize Vercel's built-in analytics to identify performance bottlenecks.

Version control

Use version control systems (e.g., Git) to track changes to your codebase. This helps you identify when issues were introduced and roll back to a stable state if necessary.

Troubleshooting Vercel Edge Functions is an essential skill for any developer leveraging this powerful platform.

By understanding common issues, following best practices, and using effective troubleshooting strategies, you can ensure your Vercel Edge Functions run smoothly and deliver top-notch performance for your web applications.

Read: Best Practices For Safety And Privacy Vercel Deployment

Edge Config


Web optimization is a critical component of any successful online presence. While Google Optimize has been a trusted solution for A/B testing and optimization, Vercel Edge Functions offers an exciting alternative to elevate your website's performance, reduce complexity, and save costs.

Transition to Vercel Edge Functions and experience the power of a global content delivery network, serverless functions, and advanced routing capabilities. In a world where performance and user satisfaction are paramount, Vercel is your key to staying ahead of the curve.

Stay tuned with Kapsys for more actionable insights!