HTML Code Viewer

The preview in the right panel is a close representation of how your code would appear in a browser. If something looks unexpected, check that your HTML tags are properly closed.

The HTML you paste is placed inside an iframe isolated with the 'sandbox' attribute. This isolation allows the code to run while blocking its access to the rest of the site, cookies, or other tabs — meaning even untrusted code can be safely tested.

• You paste your HTML (which can also include CSS/JavaScript) into the code box.
• When you click 'Update Preview,' the code is passed to an isolated iframe.
• The iframe renders the code in an environment isolated from the main page, thanks to the 'sandbox' attribute.
• The result is displayed visually in the preview area on the right.
• Edit the code and click the button again to update the preview.

When you paste an embed iframe snippet or a simple HTML/CSS experiment, the result appears instantly in the right panel, so you can check how it will look before adding it to your live site.

• Test how an embed code (like an iframe widget) will look on your site before publishing it here.
• The preview doesn't update automatically on every change — remember to click 'Update Preview' after editing your code.
• Because the preview area is isolated, any scripts in your code cannot affect or read the rest of your page.

During web development, seeing how a piece of HTML or an embed code will look on the real site usually means adding the code to a live environment first — which can waste time and, in the case of faulty code, break the site's appearance. This tool eliminates that risk by letting you test the code in an isolated environment.

At the core of this tool is the 'sandbox' iframe feature offered by browsers. This feature fully isolates the content inside an iframe outside a specific set of permissions; by default, no capability is granted beyond running scripts — no access to the parent page, no form submission, no opening new windows.

This design choice is deliberate: it offers a space where users can test even code they don't trust, while protecting the actual site (and the user's cookies and session data) in the process. Many professional code-sharing platforms (like CodePen-style tools) follow the same isolation principle.

The preview doesn't refresh automatically with every code change; instead, it's triggered manually with the 'Update Preview' button. This keeps performance smooth and gives the user control over when code actually runs, rather than executing it accidentally before it's finished.

This tool is useful for testing embed widgets, quickly trying out an HTML/CSS idea, safely inspecting code shared in a bug report, or simply seeing how HTML renders as part of a learning process.