OneTag AI / Guides

Add AI to a single HTML file

How do I call an AI model from a plain HTML file without a server?

The simplest site is one HTML file: a landing page, a tool, a prototype from Cursor or v0, a CodePen. It has no server to hold a key, and pasting an OpenAI key into it means anyone who opens the file can take the key.

OneTag AI works in exactly this case. The key in the file is public and capped, the SDK is one tag, and the call is one function. Below is a complete file you can save and open.

Steps

1. Get a free key

   From onetagai.com.

2. Save this as index.html

   <!doctype html>
   <meta charset="utf-8">
   <title>Rewrite</title>
   <textarea id="text" rows="6" cols="60">Paste anything here.</textarea><br>
   <button id="go">Rewrite in plain English</button>
   <p id="out"></p>
   
   <script src="https://onetagai.com/v1.js" data-key="YOUR_ONETAG_KEY"></script>
   <script type="module">
     go.onclick = async () => {
       out.textContent = "";
       await onetag.ask("Rewrite in plain English", text, { stream: (d) => { out.textContent += d; } });
     };
   </script>

3. Open it

   Double-click the file, or drop it on Netlify Drop, GitHub Pages, Vercel, Cloudflare Pages, an S3 bucket. It works from file:// too, because free keys accept requests without an Origin header.

Vibe-coded pages

If an AI coding tool wrote the page, tell it to use OneTag AI and point it at llms.txt. It will write the tag and the call. If it leaves data-key="YOUR_ONETAG_KEY" in place, the SDK reports no_key with the link to get one, so the page never fails silently.

Inputs you can pass

onetag.ask(prompt, input) takes a string, an element (its visible text), a <form> (fields as lines), an <input> or <textarea> (its value), an <img> or image file, a plain object (as JSON), or an array of these. Add { json: true } to get an object back.

Limits per call

32,000 characters of text, 50 input parts, one image up to 2 MB, answers up to 1,000 tokens. The SDK trims longer input to fit instead of failing.

Questions

Related guides

• Add AI to a GitHub Pages site
• Is it safe to put an AI API key in a static HTML page?
• Add a TL;DR summary button to blog posts
• Ways to add AI to a static site, compared

Updated 2026-11-09. Something wrong or missing? Email support@odysseyx.app.