How to put an app you built with Codex online

Your app works on your computer, and now you want other people using it. To put an app you built with Codex online, it needs a host: a place online where a copy of it runs, with a link you can send. Codex can do most of that setup, once you connect it to a host and name that host when you ask. I build fline, hosting for apps people build with Claude Code or Codex on their own computer, so this page shows the steps with fline, covers OpenAI's own option, and says plainly what fline does today. If you use Claude Code instead, the same steps are in how to get your Claude Code app online.

Why can only I open my app right now?

When Codex starts your app on your computer so you can try it, the app runs there, at an address only your computer can open. Nobody else can reach it, and it stops when your computer sleeps or the app is closed. A host runs a copy of your app where other people can reach it and gives it a link you can send. More in why an app only works on your computer.

Can Codex put my app online by itself?

Sometimes, through OpenAI's own Sites. OpenAI's guide to Sites says it lets you build, host and share a website by describing it in ChatGPT or Codex, and that it can also host a compatible project you've already built. You create, publish and manage a site in ChatGPT on the web or in the ChatGPT desktop app, which can start one from a compatible project on your computer. OpenAI says Sites has no place of its own to manage sites in the Codex CLI, which runs in Terminal, or in Codex's editor extension, though you can still use those to change and test your project before you publish it.

OpenAI also says Sites runs sites in its own setup, and that some frameworks (the toolkits apps are built on), databases and background services aren't supported. Who can open a site depends on your ChatGPT account and its settings, and OpenAI's Help Center has the current plans and limits.

OpenAI's guide to putting an app or website online with Codex shows another route: Codex uses Vercel's plugin, an add-on for Codex, to put a preview of your site on Vercel, another host, and hands you the link.

So if your app fits Sites and you'd like to keep everything in ChatGPT, Sites may suit you. If you'd rather put the project in your folder online from Codex itself, connect Codex to a host and name that host when you ask, or Codex may pick a different one. If you also use Claude, can Claude host my website? covers what each part of Claude can put online, and where should I host my app? compares the other kinds of host.

How to put your Codex app online with fline, step by step

There are four steps, and none of them is coding.

1. Get an account. fline is in private beta, and accounts are opened by hand, a few at a time. Ask for early access with your email address, and fline emails you when your account is open. Create your account with the same address, then open your fline dashboard once to set it up. Getting your account walks through each step.

2. Connect Codex. Your fline dashboard shows two lines under Codex, with a button to copy them. Paste them at the end of Codex's settings file, a file called config.toml in a folder named .codex inside your home folder (create the file if it isn't there), and save it. Then open your computer's Terminal app, type codex mcp login fline and press Return, and approve fline in your browser. Connect Codex has every step, including what to do if your text editor changes the quote marks.

3. Ask. In your project folder, start Codex and tell it:

Put this project online with fline.

Codex packs up a copy of your project folder and sends it to fline, and it may ask your permission first, which is expected. fline works out how to build and run your app, so there are no setup files to write. To do that, fline sends parts of your code to an AI model made by OpenAI, and the passwords and keys you save on fline never go to that model.

4. Send the link. When your app is ready, your dashboard shows its link, and you can ask Codex for it too. Check it on your phone, then send it to your first users. Put your app online walks through a whole first launch. It's written for Claude Code, and the steps are the same.

What about keys, a database and my own web address?

Each of these can need a small step from you.

• Keys. If your app uses a password or key, like a payment key, Codex gives you a link to a private fline page. You type the key there, not in the chat, and Codex sees that you did it, not what you typed. The page works once, for 10 minutes. If you paste a key into the chat instead, Codex sees it. Is it safe to give Claude Code your API keys? is written for Claude Code, and the same habits apply with Codex.
• A database. If your app needs to remember things, like sign-ups or bookings, fline can create the database your app needs, and runs it. Codex can ask fline for it. More in a database for your app.
• Your own web address. The link starts out long, ending in apps.dev.fline.sh. You can also put your app at a web address you own, like www.yourbakery.com, by adding one record at the company where you bought it. fline sets up the padlock and renews it. Use a web address you own has the steps.

What if something breaks after it's online?

Ask Codex again. If a launch or an update fails, your fline dashboard says so, and one button copies the problem so you can paste it into Codex. Codex can see what went wrong, try a fix, or put an earlier version back, though fline can't promise it finds the fix. When you update your app later, the current version keeps running while the new one is prepared.

If your app works on your computer but looks blank or broken online, works on your computer, broken online lists the usual causes, and they're the same with Codex. For more things to say, what to say to Claude Code has prompts to copy, and you can give Codex the same prompts. Where one says CLAUDE.md, write AGENTS.md instead: that's the file of instructions Codex reads before it starts work.

What if I used Codex Cloud?

Bring its changes into the folder on your computer first, then ask Codex there to put the project online with fline. fline needs your project as a folder on your computer, sent by Codex running there, and a Codex Cloud task isn't a path we've tested. OpenAI describes Codex Cloud as running coding tasks in the cloud, on projects you pick from GitHub, and you save the results back to GitHub when you're ready. To get them, you can ask Codex on your computer to bring in those changes from GitHub.

The tested path is the one on this page: Codex's settings file, one sign-in line in Terminal, then asking Codex in your project folder. Other ways to use Codex, such as its editor extension and the ChatGPT desktop app, aren't part of that tested path yet.

Where fline fits

fline is hosting for apps you build with Claude Code or Codex on your own computer: the step after it works. It's independent, and isn't made by OpenAI or Anthropic. Codex is tested with fline from start to finish, and so are Claude Code in Terminal and the Code tab of the Claude desktop app. fline is free during the private beta, with no card. That doesn't cover Codex itself: you use it with your own ChatGPT account or OpenAI key, as usual.

A few things it doesn't do yet. Your project has to be a folder on your computer, so fline doesn't take an app straight from a chat, an app builder or a Codex Cloud task today. The link is public, so an app that holds private information needs its own sign-in. During the beta every app runs on one rented machine with no spare, with no uptime promise and no backups you can count on, so keep your own copy of anything you can't lose. A checklist before people use your app covers what to check before you send the link, and what fline does today has the full list, with a date on it.

Built it with Codex, and it runs on your computer? Ask for early access.

Questions people ask

Can Codex host my website?

Yes, if your website fits OpenAI's Sites. Sites can host a website you make in ChatGPT or Codex, including a compatible project you've already built, and OpenAI says you publish and manage it in ChatGPT on the web or in the desktop app. OpenAI also says some frameworks, databases and background services aren't supported there. You can also connect Codex to a host such as fline and ask it to put the project in your folder online.

How do I share my Codex app with other people?

Put it on a host, then send the link. While your app runs only on your computer, it opens only for you. On a host such as fline, your app gets a link that opens on any phone or computer, and you can put it at a web address you own, like www.yourbakery.com. The link is public, so give your app a sign-in if it holds private information.

Can Codex put my app on Vercel?

Yes. OpenAI's own guide shows Codex using Vercel's plugin to put a preview of a website on Vercel and hand back the link. Vercel is a separate host from fline. If you'd rather use fline, connect Codex to fline and name fline when you ask, as in "Put this project online with fline."

Can I use fline from a Codex Cloud task?

Not as a tested path today. fline needs your project as a folder on your computer, sent by Codex running there, and a Codex Cloud task works on your project from GitHub, in the cloud. Bring the task's changes into the folder on your computer first, then start Codex there and ask it to put the project online with fline.

Do I need to know how to code to put my Codex app online?

No. With fline a few steps need you, and none of them is coding. You open your fline dashboard once, paste two lines from it into Codex's settings file, type one line in your computer's Terminal app, and approve fline in your browser. You type any passwords or keys on a private fline page, and add one record at your domain company if you want your own web address. Everything else, you ask Codex for in plain words.

What does it cost to put my Codex app online with fline?

fline is free during the private beta, with no card. There's no price and no billing yet, and fline's terms say any future price applies only from then on, so your time in the beta won't be charged later. Codex itself is separate: you use it with your own ChatGPT account or OpenAI key, as usual.