What the sandbox is good for
Trying an idea before it goes into a real project, checking how a snippet from a tutorial behaves, testing a layout on your phone, or showing a colleague exactly what you mean. Because every change shows up as you type, it is also a comfortable way to learn HTML and CSS one line at a time.
The sandbox accepts a single HTML document. Styles can live in a <style> tag and scripts in a <script> tag, and you can load fonts or libraries from public CDNs. If you have an .html file already, drop it on the editor or use Open file.
How the isolation works
The preview runs in a sandboxed frame, and a saved pad is served with its own restricted origin. Code in a pad cannot read your HTMLpad drafts, act on other pads or reach the editor around it. Pages that ask for passwords or card numbers are refused when you save, because that is how HTML hosts are most often abused.
From sandbox to link
Saving turns the sandbox into a pad with its own address. Free pads stay online for 90 days, and saving again resets the count. From the editor you can also copy an embed code to show the pad live on your own site, or download the file as .html to keep it.
Frequently asked questions
What is an HTML sandbox?
An HTML sandbox is a place where you can write HTML, CSS and JavaScript and run it straight away in an isolated frame, so the code cannot affect the page around it or your own device.
Do I need an account to use the sandbox?
No. You can write and preview as much as you like without signing up. Saving gives you a link, and leaving an email is optional.
Can I use JavaScript in the sandbox?
Yes. Scripts run inside the preview frame. They cannot read HTMLpad's data or other pads, and password or card fields are not allowed in saved pads.
How do I share what I made?
Save the pad to get an address such as HTMLpad.org/your-name/. You can send that link, embed the pad on your own site, or let others remix it into a copy of their own.