Is HTML actually compiled?

No. HTML is a markup language that browsers parse and render directly; there is no compile step. An online HTML compiler runs your HTML, CSS and JavaScript in a browser engine and shows the result, which is what people usually mean by compiling HTML.

Can I run JavaScript in this HTML compiler?

Yes. Code in the JS tab runs inside the output frame when you press Run. Output from console.log(), warnings and uncaught errors appear in the Console panel below the result.

What is the difference between the HTML compiler and the HTML editor?

Both run the same engine. The compiler runs your code only when you press Run and opens the console by default, which suits testing and debugging scripts. The editor updates the preview as you type, which suits designing a page.

Is my code sent to a server?

No. Everything runs in your browser. Your code is saved in your browser's local storage so it is still there when you come back, and you can download it as an .html file.

Why doesn't my external script or image load?

The output runs in a sandboxed frame with its own isolated origin. Resources from full https:// URLs, such as a CDN, work normally. Relative paths like images/logo.png don't, because your files aren't on a server.

HTML Compiler Online

Run HTML, CSS and JavaScript code and see the result and console output instantly.

PreviewAuto preview is off — press Run

<h1>Shopping list</h1>
<form id="add">
  <input id="item" placeholder="Add an item" aria-label="Item">
  <button>Add</button>
</form>
<ul id="list"></ul>

body { font-family: system-ui, sans-serif; margin: 24px; }
ul { padding-left: 20px; }
li.done { text-decoration: line-through; color: #64748b; }

const items = ["Milk", "Bread"];
const list = document.getElementById("list");

function render() {
  list.innerHTML = "";
  for (const text of items) {
    const li = document.createElement("li");
    li.textContent = text;
    li.onclick = () => li.classList.toggle("done");
    list.append(li);
  }
  console.log("Rendered", items.length, "items:", items);
}

document.getElementById("add").addEventListener("submit", (event) => {
  event.preventDefault();
  const input = document.getElementById("item");
  if (input.value.trim()) items.push(input.value.trim());
  input.value = "";
  render();
});

render();

Output from console.log() and JavaScript errors appears here.

Ctrl/⌘ + Enter runShift + Alt + F formatEsc then Tab leave editor Runs in your browser — nothing is uploaded

How to use the HTML compiler

Put your markup in the HTML tab, styles in CSS and scripts in JS.
Press Run or Ctrl + Enter to compile and run the code. The result appears in the output frame.
Read console.log() output and runtime errors in the Console panel. Fix the code and run it again.
Turn on Auto preview if you want the output to refresh while you type, or Download HTML to save everything as one file.

What “compiling” HTML really means

HTML isn't compiled like C or Java. Browsers read HTML and CSS directly and run JavaScript with a just-in-time engine. When people search for an HTML compiler online, they want exactly what this tool does: take HTML, CSS and JavaScript, run them together in a real browser engine and show the result — plus the errors when something breaks.

Your code runs in a sandboxed frame with its own isolated origin, so scripts can't touch this website or your data here. Nothing is uploaded; it all happens in your browser.

Features

Separate HTML, CSS and JavaScript tabs with syntax highlighting and line numbers.
Run on demand, with a console for logs, warnings and uncaught errors.
Format all three files with one click; your code is autosaved in the browser.
Open the output in a new tab or full screen, or download it as a single file.
Works on phones, with tabs for each file and the output.

When to use it

Test a JavaScript snippet against real DOM elements before adding it to a project.
Debug a bug report: paste the reproduction, run it, and read the console.
Practise for coding exercises and interviews without setting up a local project.

For example, running this in the JS tab shows why mixing strings and numbers gives a surprising total:

JavaScript

const prices = [19.99, 5, "12"];
const total = prices.reduce((sum, p) => sum + p, 0);
console.log(total); // "24.9912" — the string "12" was concatenated
console.log(prices.map(Number).reduce((a, b) => a + b, 0)); // 36.99

Related HTML tools

Designing a page rather than debugging it? The online HTML editor refreshes the preview as you type. To just look at existing markup, open it in the HTML viewer, and before publishing, run it through the HTML validator to catch unclosed tags and missing alt text. Writing Python instead? Try the Python online compiler.

Frequently asked questions

Is HTML actually compiled?: No. HTML is a markup language that browsers parse and render directly; there is no compile step. An online HTML compiler runs your HTML, CSS and JavaScript in a browser engine and shows the result, which is what people usually mean by compiling HTML.
Can I run JavaScript in this HTML compiler?: Yes. Code in the JS tab runs inside the output frame when you press Run. Output from console.log(), warnings and uncaught errors appear in the Console panel below the result.
What is the difference between the HTML compiler and the HTML editor?: Both run the same engine. The compiler runs your code only when you press Run and opens the console by default, which suits testing and debugging scripts. The editor updates the preview as you type, which suits designing a page.
Is my code sent to a server?: No. Everything runs in your browser. Your code is saved in your browser's local storage so it is still there when you come back, and you can download it as an .html file.
Why doesn't my external script or image load?: The output runs in a sandboxed frame with its own isolated origin. Resources from full https:// URLs, such as a CDN, work normally. Relative paths like images/logo.png don't, because your files aren't on a server.