HTML Viewer Online — Free In-Browser HTML Sandbox | Online Gallery
Preview offline HTML webpages & email templates in sandbox. Safely preview offline HTML webpages, email newsletters, and templates in an isolated browser sandbox.
What is HTML Viewer and what does it do?
Preview offline HTML webpages, email newsletters, and templates inside a safe, sandboxed browser viewport.
- Live sandboxed rendering of HTML documents.
- Toggle between rendered page and syntax-colored source code.
- Inspect email templates without email client overhead.
How does HTML Viewer work?
Loads file contents into an isolated iframe sandbox with restricted permissions.
100% private: all processing happens locally in your browser using client-side WebAssembly, WebCrypto, WebAudio, and HTML5 Canvas. Your files are never uploaded to any server.
Who needs HTML Viewer?
Web Designers & Email Marketers
Preview responsive newsletter layouts and static templates locally.
Supported file formats
HTML Document & Webpage Sandbox opens and processes the following file extensions directly in your browser:
.html.htm.xhtmlHow to use HTML Viewer — step by step
- 1
Select HTML
Open your .html or .htm file.
- 2
Toggle Modes
Switch between Live Sandbox View and Raw Source Code.
Frequently asked questions
Is the HTML execution safe?
Yes, it runs inside a restricted sandboxed iframe.
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