HTML Viewer
Paste HTML to preview it rendered in a sandboxed frame, then format the source — all locally in your browser, nothing uploaded.
Preview HTML without running its JavaScript
Paste a document or fragment into the editor and the frame next to it shows its HTML and CSS. This is useful to check an email layout, a scraped fragment, generated markup or a small component without having to save a file first.
The preview uses a sandboxed iframe with scripts disabled. Inline styles and style attributes still affect the rendering, but <script> elements do not execute. The Format action can also re-indent the source before you inspect it.
What the preview can and cannot tell you
The frame shows how the markup looks with the current browser at the size of the preview. It is a fast visual check, not a cross-browser test, accessibility audit, responsive device lab or email client emulator. What looks correct here might still be different in Safari, an older embedded browser, Outlook, or a restrictive content-security-policy environment.
Scripts are disabled, so interactive widgets, client-side templates and code that alters the DOM will not run. Test these behaviors in a controlled development environment where you know the code and its dependencies.
Remote resources are still remote
The HTML source is not uploaded for conversion, but assigned to the local preview frame. But markup referencing an external image, stylesheet, font, iframe or other URL may cause your browser to ask for that resource. The remote host then receives normal request metadata such as your IP address and user agent.
Remove remote URL or replace it with a local placeholder for a self-contained preview. Blocking scripts is a significant boundary, but not the same as blocking all network requests.
Format carefully
The built-in formatter is intended to make nesting readable. It may change meaningful whitespace between tags, so keep the original when working with inline text, email markup, or templates. For a dedicated explanation of those limits, see the HTML Formatter.
FAQ
Why doesn't my JavaScript run?
Iframe sandbox does not allow scripts to run. The viewer is for inspecting HTML and CSS, not for executing untrusted or interactive code.
Can the preview fetch external images or styles?
Yup. If the pasted markup includes remote URLs, the browser may fetch them. You can delete those references if you want a self-contained preview.
Is this a validator?
Nah. The browser may be able to recover from bad HTML while rendering it. If you need to check the conformity to standards, use an HTML conformance checker.