# How to test Netlify Functions locally

> Learn how to test Netlify Functions locally with the Netlify CLI: run netlify functions:serve, hit them on port 9999, and pick up your environment variables.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2022-04-03 | Topics: [Services](https://flaviocopes.com/tags/services/) | Canonical: https://flaviocopes.com/netlify-functions-testing/

I have quite a few sites hosted on [Netlify](https://flaviocopes.com/netlify/), and some of them use a feature called [Netlify](https://flaviocopes.com/netlify/) Functions.

This is probably - of course after the incredible static hosting service they provide - my favorite feature.

You add a [JavaScript](https://flaviocopes.com/javascript/) file with an exported function to handle the request to the URL, and you're set. 

You can do pretty much anything and I use them as little utilities to visualize internal data I need or to perform operations that "connect the dots" aka glue different tools I use to run my business. 

> If you want to learn more about them, check out my [Netlify Functions tutorial](https://flaviocopes.com/netlify-functions/).

In this post I want to talk in particular about how to test Netlify functions locally.

I had this need the other day when I wanted to do a change to a Netlify Function that was live running to handle signups to my Bootcamp and I didn't want to disrupt my operations, causing problems to a customer.

I did test this "live" prior to opening signups to see if things were running as expected, but now I had a different need. 

So here's what I did.

I first installed the Netlify CLI 

```
npm install -g netlify-cli
```

Then from the website folder I ran

```
netlify functions:serve
```

This served the serverless functions locally, on port `9999` so I just had to reach them using a URL like

```
http://localhost:9999/.netlify/functions/<name>
```
 
and I was able to test them by faking a POST request using [Insomnia](https://insomnia.rest).

In this way deploying the changes to production was much less stressful.

This way of testing the functions also grabs any [Netlify environment variables](https://flaviocopes.com/netlify-functions-env-variables/) you might have set in the Netlify Dashboard, so it just works like you were running it on Netlify.