How to Use Netlify Serverless Functions

Serverless functions have revolutionized the way modern web developers build back-end logic for their front-end applications. Among the many platforms embracing this trend, Netlify stands out with its powerful, yet easy-to-use serverless function support. Whether you’re creating a dynamic form handler, connecting to an API, or processing background tasks, Netlify serverless functions offer a fast and scalable solution without the overhead of setting up a traditional server.

TL;DR

Netlify serverless functions allow you to run backend code directly from your Git repository without managing infrastructure. By placing JavaScript or TypeScript files in a specific directory, you can deploy functions alongside your frontend with ease. They are perfect for handling API requests, form submissions, and interacting with databases or third-party services. This guide walks you through everything from setting up your first function to deploying and testing it in the cloud.

What Are Serverless Functions?

At their core, serverless functions are snippets of backend code that execute in response to events, like HTTP requests. With Netlify, these functions are deployed on AWS Lambda under the hood, but you don’t have to worry about managing any infrastructure or configurations—just write the function and deploy it!

Some key characteristics of Netlify serverless functions:

• Run on demand, billed only for usage
• Can be written in JavaScript or TypeScript
• Deployed alongside your frontend
• Automatically scale as needed

Getting Started with Netlify Functions

To begin using Netlify functions, you’ll need:

• A GitHub, GitLab, or Bitbucket account
• A Netlify account
• A frontend project (React, Vue, Svelte, or just plain HTML)
• Node.js installed locally

Once you’re set up, follow these steps:

1. Create a Netlify Project

If you haven’t already, push your frontend project to Git and link it to a new Netlify site:

1. Log in to Netlify
2. Choose “New site from Git”
3. Connect your repository and select the build settings

2. Set Up the Functions Directory

Inside your project root, create a folder to contain your functions. By default, Netlify looks for a directory called netlify/functions, but you can specify a custom one in your netlify.toml config.

mkdir -p netlify/functions

Then, add a simple function:

// netlify/functions/hello.js
exports.handler = async function(event, context) {
  return {
    statusCode: 200,
    body: JSON.stringify({ message: "Hello from Netlify!" })
  };
};

And configure your netlify.toml file (if using a non-default directory):

[functions]
  directory = "netlify/functions"

3. Test Locally with Netlify CLI

Use the Netlify CLI to test your functions locally before deploying them.

npm install -g netlify-cli
netlify dev

Your function will be accessible at http://localhost:8888/.netlify/functions/hello

Advanced Function Features

Netlify offers far more than just basic “hello world” functions. Let’s explore some of the advanced capabilities that make serverless development even more powerful:

1. Accessing Environment Variables

Environment variables help keep sensitive information, like API keys and credentials, secure. Define your environment variables in the Netlify UI or in netlify.toml under the [build.environment] section.

console.log(process.env.MY_SECRET_KEY);

2. Parsing JSON Requests

Netlify serverless functions can handle incoming POST requests, which makes them great for form handling and API endpoints.

// netlify/functions/submit.js
exports.handler = async function(event) {
  const data = JSON.parse(event.body);
  return {
    statusCode: 200,
    body: JSON.stringify({ received: data })
  };
};

3. Scheduled Functions

Want a function to run on a regular schedule rather than on-demand? Netlify offers scheduled functions through its background function feature. Add a schedule field in your export:

exports.handler = async function(event, context) {
  console.log("This runs every day!");
  return {
    statusCode: 200,
    body: "Scheduled job complete"
  };
};

exports.schedule = "0 12 * * *"; // Every day at noon UTC

Deploying and Testing Functions

Once you’re confident with your local functions, push your code to GitHub. Netlify will automatically deploy the updated code, including any functions you’ve added or modified. To see your function live:

Navigate to:

https://your-site.netlify.app/.netlify/functions/hello

Here are some ways you can test your deployed functions:

• Use Postman or curl for various HTTP methods
• Integrate them into your JavaScript frontend using fetch()

Common Use Cases

Not sure how serverless fits into your project? Check out these popular use cases:

• Form submissions – Handle net-new or custom form data securely
• Email notifications – Trigger transactional emails using APIs like SendGrid or Mailgun
• Authentication – Manage login tokens, handle OAuth callbacks
• Third-party APIs – Hide API keys and mediate external services
• Data processing – Transform, filter, or enrich data before displaying it

Best Practices for Netlify Functions

Here are a few tips to keep your functions fast, secure, and reliable:

• Limit payload sizes: Keep your data minimal to speed up function execution
• Use environment variables: Never hard-code secrets or keys
• Handle errors gracefully: Return clear status codes and messages
• Monitor logs: Use Netlify’s function log UI or CLI logs to debug
• Version control: Treat your functions like any other part of your codebase

Deploying from Monorepos or Custom Structures

If you’re using frameworks like Next.js or a monorepo setup, you may have a different directory structure. You can adjust the function path in your netlify.toml:

[functions]
  directory = "apps/my-app/netlify/functions"

This flexibility makes Netlify functions usable in almost any project structure without rethinking your architecture.

Debugging and Logging

To make debugging easier, Netlify provides:

• Function logs in the Netlify dashboard
• console.log outputs visible during local development
• Return JSON-formatted error messages in production for better front-end handling

Example:

exports.handler = async () => {
  try {
    // risky operation
  } catch (err) {
    console.error("Something went wrong", err);
    return {
      statusCode: 500,
      body: JSON.stringify({ error: "Internal server error" })
    };
  }
};

Closing Thoughts

Netlify serverless functions open the door for developers to create powerful, dynamic backend features without needing to manage servers or deployment pipelines. By integrating seamlessly into your frontend project, they support faster development and a streamlined deployment workflow.

Whether you’re building a hobby project or scaling a SaaS product, serverless functions provide the flexibility and scalability you need without the headache. Start small—maybe with a contact form, analytics log, or webhook—and you’ll quickly discover how server