My app works on my laptop but not for my friends. Why?

Localhost is the name a computer uses for itself. When you run your app while building it, it usually lives at an address like localhost followed by a number. That address means "this computer".

So when you open it, you see your app. When a friend opens the same link, their computer looks for an app on itself, finds nothing, and shows an error. Nothing is broken. The link was never meant to leave your machine.

A live website runs on hosting, a rented computer on the internet that stays switched on and answers anyone who visits. Your laptop sleeps, moves between networks and is not set up to take visitors from outside.

You deploy it, which means copying the latest version onto hosting. How you do that depends on how you built it:

• Built inside an app builder: there is often a publish or deploy button, and the builder may host the app for you. Look for a live address after you press it.
• Built as code on your laptop: you need a hosting service and a way to send your code to it. Many hosting services connect to where your code is stored and deploy each new version for you.

Each deploy replaces what visitors see. So a broken change goes live too. Test after every deploy, not just the first.

Not to start. A custom domain is your own web address, such as yourapp.com instead of a long address the host gives you. You rent it from a domain seller, then point it at your hosting by changing a few settings.

It makes the app look more trustworthy and easier to remember. But the free address from your host works fine for testing with friends. Add the custom domain once the app works live.

Because some things exist only on your laptop. The common ones, in our reading of early apps:

• Secrets and settings: passwords and keys your app uses to talk to other services. On your laptop they sit in a local file. Live, you usually have to add them again in the hosting service's settings, often called environment variables.
• Your local database: if your data sits on your laptop, the live app cannot see it.
• Addresses written into the code: if the code still points at localhost somewhere, that part breaks live.

Here is an illustrative example, not a real founder. Say your app shows a list of recipes on your laptop, but live it shows an empty page. The recipes were stored in a database on your laptop, and the live app had no way to reach it. Moving the data to a hosted database fixes it.

1. The link starts with https and your live address, not localhost.
2. It opens on your phone with wifi off, so you know it works from outside your network.
3. You can sign up and log in on the live version, not just on your laptop.
4. Every secret your app needs is set in the hosting settings.
5. You opened it in a private browser window, so you are not seeing a version saved on your computer.

If you are about to show it to more than friends, what you might be forgetting before launch covers the wider list.

If you are still changing everything every hour, deploying can feel like extra work. That is fair for a few days. The missing fact is whether real people can use what you built. You only learn that once it is live, so deploy early and deploy small.

Not sure which builder, hosting and database to use together? Stack Picker suggests one set of tools you can build and run alone: one tool for each layer of your app, each with a reason. Which tools to build with as a non-technical founder explains the choices in more depth.

Deploy your app once, even if it is unfinished. Open the live address on your phone with wifi off. Sign up, log in and do the one main thing your app is for. Write down the first step that fails and fix only that one.