Build a web app with a coding agent, starting from nothing

You have an idea for a web app and no developer. This page takes you from that to a live address people can sign in to, using a coding agent: a program on your computer that writes the code and runs the commands for you. The route it leads with needs no terminal. You install two things, paste one prompt, answer the agent in plain words, and say yes when it asks permission. Budget an hour the first time; most of it is waiting for installs.

What you will not do on this page: rent a server, buy or renew a security certificate, build a login, set up a database, or learn how any of those work. They come with the app. Your part is the idea and a few clicks.

nerdsystem itself is free to start: one app, up to 1,000 people signing in a month, and no card. The agent is the only thing you may pay for; the table below says what each one charges.

Would you rather be taught as you go? The free course is six short lessons with your agent as the teacher. It starts with the same two installs as this page, so do Step 1 and Step 2 here, then take the course's prompt in place of Step 3.

What a coding agent is, and what it is not

A coding agent is a program that runs on your computer, reads and writes the files in a folder, and runs commands in that folder. You talk to it in plain language: "build me a booking page for my dog-walking business". It writes the code, runs it, reads the errors, fixes them, and asks you only when it needs a decision.

A chat website is not a coding agent. ChatGPT and claude.ai can write code, but they cannot run anything on your computer. They hand you commands to type, which is the part you are trying to avoid. The four programs in the table below can run things themselves.

Some agents live in a terminal, the plain text window where commands run. You do not need one for the first route below. The terminal routes come after it, with how to open one, for people who prefer them.

Step 1: Get an agent

The four below are alternatives. You need one of them, not all four. If you have no preference, take the first: it is the route this page walks through.

Any of the four works with the prompt further down. It has been run most with Claude Code, including by people who had never used a terminal. Prices and commands were checked against each vendor's own pages on 2026-11-05, and the Claude desktop steps on 2026-11-09; they change often, so if a vendor's page disagrees with this one, the vendor is right.

Gemini CLI is not in the table. Since June 18, 2026 it no longer accepts personal Google accounts; it is now for organizations with a Gemini Code Assist license, or people paying for an API key. Google's replacement for individuals is Antigravity CLI, which we have not tested with this template.

Claude Code in the Claude desktop app, with no terminal

1. Download the Claude desktop app, open the downloaded file, and follow its steps to install it.
2. Open Claude, from Applications on a Mac or the Start menu on Windows, and sign in with your Claude account. Claude Code needs the Pro plan or higher; if the app asks you to upgrade, that is why.
3. Click Code at the top of the sidebar. If the tabs show only icons, hover over one to see its name.
4. Make an empty folder for your app, in Documents for example. In the row under the box where you type, click the first control and choose the top entry under Local. Then click the folder control next to it, choose Open folder…, and pick the folder you made.
5. Leave it there. After Step 2 and Step 3, this is the box you paste the prompt into.

The same row has a mode selector. In Manual, Claude asks you before every step, and you say yes. The other modes ask less often. Anthropic's guide to the desktop app covers every click, including an older layout of the app that has no such row.

Or: Claude Code in a terminal

A terminal is the plain text window where commands run. On a Mac it is an app called Terminal: press Command and Space, type Terminal, press Enter. On Windows the equivalent is PowerShell, but for this work use Git Bash, which comes with Git for Windows. Once the agent is running you will rarely need to type in it; the agent does.

On a Mac, open Terminal, paste this line, and press Enter:

curl -fsSL https://claude.ai/install.sh | bash

It shows nothing while it downloads. Leave the window alone until it prints "Claude Code successfully installed!", then close Terminal and open it again. On Windows, open PowerShell (press the Windows key and X, then choose Windows PowerShell or Terminal) and paste this instead:

irm https://claude.ai/install.ps1 | iex

On Windows, paste with Control and V or a right-click. The Windows installer does not need administrator rights, the Mac one installs into your own user folder, and neither needs Node for itself.

To start it, make an empty folder for the app and open a terminal in that folder. On a Mac, type cd , drag the folder into the Terminal window, and press Enter. On Windows, open the folder in File Explorer, right-click an empty spot, and choose Open in Terminal or Git Bash Here. Then type claude. The first run opens your browser to sign in with your Claude account, which needs the Pro plan or higher. Anthropic's terminal guide covers every click for people who have never done this.

Or: Cursor

Download it from cursor.com/downloads. On a Mac, scroll to the macOS list and pick "Mac Universal" if you are not sure which chip your Mac has. On Windows, pick "Windows (x64) (User)" for a normal Intel or AMD PC, or "Windows (ARM64) (User)" on a Snapdragon laptop. Open it and sign in; the Free plan is enough to start.

Make an empty folder for the app, then in Cursor choose File, then Open Folder, and pick it. Press Command and I on a Mac, or Control and I on Windows, to open the Agent panel, and paste the prompt there. The agent runs the commands itself; you do not need to open a terminal.

Two things about the plans, as of November 2026. The $8 Plus plan only offers Grok models, and the Free plan has no published allowance, so a long session can run out part way. Premium at $30 a month gives four times the usage of Plus and unlocks Claude and GPT models, which are billed separately at the model's list price.

Or: Codex

The simplest route is the ChatGPT desktop app, where Codex is a mode. On a Mac, download the app from OpenAI's app page; it is built for Apple silicon, the M-series chips in Macs from 2020 on. Open it and sign in with your ChatGPT account. On Windows, install the ChatGPT app from the Microsoft Store and sign in. In the app, open the empty folder you made for the app, choose Codex from the dropdown that says ChatGPT, start a new chat, and paste the prompt as the first message. Windows runs it natively; nothing else to install.

There is also a terminal version, and it is the route for an Intel Mac, since the app is not built for one. On a Mac, paste curl -fsSL https://chatgpt.com/codex/install.sh | sh into Terminal first. Then open a terminal in the app's folder and type codex. It signs you in through your browser the first time.

ChatGPT Plus at $20 a month is the plan to assume. Free and Go list Codex only "in the desktop app, subject to rollout", which means it may not be there for you.

Or: GitHub Copilot

Install VS Code: on a Mac, open the downloaded file and drag Visual Studio Code to Applications; on Windows, run the User Installer, which needs no administrator password. Open VS Code, choose File, then Open Folder, pick the empty folder you made for the app, and select Trust (under Manage, if you see it).

Hover over the Copilot icon in the bar at the bottom of the window, choose "Use AI Features", and sign in with a GitHub account (free to create). If you have no Copilot plan you are put on Copilot Free, with no card. Open the Chat view (Control, Command and I on a Mac; Control, Alt and I on Windows), press the plus sign for a new chat, check that the control labelled Agent says Agent, and paste the prompt.

Copilot Free gives you 2,000 code completions a month and an allowance of agent use that GitHub does not publish a number for. If you run out, Pro is $10 a month plus usage.

Step 2: Install Node, the one thing you do yourself

Node is the program that runs the build tools behind every web app, and it is what installs the nerdsystem command. Every agent here needs it for this job, even the ones that did not need it to install themselves.

Go to nodejs.org/en/download and press the download button under the heading that ends in LTS; it says "macOS Installer" or "Windows Installer". Ignore the smaller link offering a newer alpha version. Run the installer and accept every default. On a Mac it asks for your Mac password. On Windows, click Yes when Windows asks to allow the install, and leave the box about automatically installing extra tools unticked, since it pulls in a lot you do not need. That gives you node and npm. nerdsystem needs Node 22.12 or newer; the LTS button gives you a newer version than that.

Then quit your agent and open it again. A program that was already open before the install does not know Node exists yet. The agent may also ask you to install git; say yes and accept the defaults.

Step 3: Say what the app should do, in one sentence

Describe it the way you would to a friend. The agent asks about the rest as it goes.

• "A booking page for my dog-walking business where clients pick a slot and I see the day's list."
• "A reminders app: I add a chore and a day, and it emails me that morning at the address I signed up with."
• "A roster for my climbing club with a sign-up form and a members-only page."

Three things are already decided, so you do not need to mention them. People sign in with an email and password, the app has a database and file storage, and it is hosted for you. Leave the colour scheme, the logo, and the second feature for later. The first version should be the one screen that makes the idea real.

Step 4: Copy the prompt and paste it into your agent

Fill in the two boxes, press Copy, paste the text into the box where you type to your agent, and press Enter.

What happens after you paste it

The agent works through the prompt and talks to you in plain words. The sequence is the same with every agent:

1. It installs the nerdsystem command. If Node is missing it stops and tells you, which is why Node comes first.
2. It sends a sign-in email to the address you typed above. Click the link in it and press Approve on the page that opens. That signs the agent in as you. The link works once and lasts 15 minutes.
3. It creates the app in a new folder and installs the app's parts. This is the slow step the first time, one to three minutes.
4. It builds the first feature from your sentence, asking only what it cannot decide.
5. It runs nerd check, which looks for the mistakes agents make, such as a secret key left in the code. If something is found, the agent reads the report and fixes it.
6. It runs nerd deploy and gives you the live address, something like https://you-booking.nerdsystem.app.

When the agent asks permission to run a step, say yes. Some agents ask every time, some only for steps they consider risky. Ten to fifteen minutes is typical from paste to live address.

When the agent gets stuck

Agents get stuck in the same few places. Each one has a sentence that gets it moving again.

If nerd check found a key in the code, the agent will ask you to set it. Open the app in the dashboard and add it under Settings, or run nerd secret set NAME and paste the value. Either way it stays out of the code. If none of these fit, copy what the agent printed and ask it: "what does this mean and what should we do?" That works more often than it sounds like it should.

What you have now

A web app at its own address, with sign-in that works. Open the address and sign up as the first user; that account is yours. Then open the dashboard, find the app, and under the Auth tab make yourself the admin.

Your code is saved on nerdsystem with every deploy and every time your agent runs nerd save, so a lost laptop does not lose the app. Changes since the last deploy or save are only on your computer. If you also want it on GitHub, say "put this on GitHub".

It is yours to take. The code is on your computer, and a copy of every deployed version can be downloaded from the dashboard. The database exports as a file, from the dashboard or with nerd db export. Nothing in it is specific to nerdsystem except the sign-in, which is a service we run.

The dashboard shows every deploy, the database, and the app's logs. For the next change, open your agent in the app's folder and say what you want. When it is done, say "run nerd check, then nerd deploy". Each deploy is checked the same way as the first.

What it costs

nerdsystem is free to start: one app, up to 1,000 people signing in a month, and the sign-in, database, storage, and checks included. Pro is $39 a month when you want more apps or your own domain name. Paid plans cancel any time from Billing, effective at the end of the period you paid for, and a first paid plan is refunded in full if you ask within 14 days of the first payment.

The agent is the only other thing you pay for, and the table above says what each one charges. Node is free. Apart from the agent's own account, there is nothing else to sign up for.