HTML Viewer

Real-time HTML editor and previewer. Write HTML code and see the result instantly.

Updated Dec 06, 2025

HTML Source

Loading editor…

Preview

Prototyping

Preview HTML snippets instantly

Debug inline HTML, email templates, or marketing embeds without leaving your browser. Paste code into the editor and view a sandboxed preview that refreshes on every keystroke.

Real-time editing

The split layout keeps code on the left and a live iframe on the right. You can toggle word wrap, load starter templates, or reset the editor with one click. Because the preview is sandboxed, running untrusted snippets is far safer than executing them inside production apps.

Syntax highlighting and automatic indentation help you spot unclosed tags, mismatched attributes, and stray inline styles before they ship.

Clipboard helpers
Copy the HTML source or the rendered DOM tree directly into bug reports or documentation.
Device agnostic
Open the viewer on tablets or phones to see how responsive layouts behave without deploying code.

Accelerate collaboration

Product managers, educators, and support teams can reproduce customer issues by pasting snippets exactly as received. Designers preview embed codes before sending them to engineers, reducing back-and-forth emails.

No network calls are made while editing, so confidential assets or unreleased campaigns remain inside your secure environment.

Safe experimentation
Play with new tags or browser APIs without touching production repositories.
Testing add-ons
Pair the preview with browser devtools to run accessibility audits or performance checks on the fly.

Workflow ideas

Email QA

Render MJML or Handlebars output before sending campaigns to real inboxes.

Component smoke tests

Verify isolated UI snippets exported from Storybook or design systems.

Support troubleshooting

Paste problematic embeds from tickets to reproduce bugs within seconds.

CMS previews

Share sanitized previews with marketing teams who do not have local dev setups.

Next step

Need to save your findings?

Copy the finalized snippet into the Markdown Viewer to capture notes or publish it inside internal guides.

Open Markdown Viewer

Popular combinations

Audit with Diff Checker
Compare HTML Viewer output with previous revisions to avoid regressions.
Share via QR Code Generator
Turn sanitized payloads into QR codes for offline reviews.

Frequently asked questions

How does the HTML Viewer work?

The HTML Viewer provides a real-time preview of your HTML code. As you type in the editor, the preview pane instantly updates to show you how the browser renders your markup.

Can I use CSS and JavaScript?

Yes. You can include `<style>` tags for CSS and `<script>` tags for JavaScript directly within the HTML editor. The preview runs in a sandboxed environment for security.

Is it safe to paste sensitive code?

Yes. All rendering happens client-side in your browser. We do not store or transmit your code to any server.

Does it support HTML5?

Yes. The viewer supports all standard HTML5 tags and attributes supported by your current browser.

How to use HTML Viewer

Follow these four quick steps to inspect markup or diagrams with instant previews right inside your browser—no downloads, no accounts, and no data leaving the FreeTools.run sandbox.

Step 1: Load your source data
Paste text, drag a file, or start with our curated sample to understand how the viewer workflow behaves with real inputs.
Step 2: Adjust tool options
Toggle presets, update formatting rules, or choose export preferences. All controls update in real time so you can preview the effect before committing.
Step 3: Review the live preview
Use the split-pane preview, inline validation, or diff output to confirm the transformation looks correct before you copy anything back into your project.
Step 4: Export or chain another tool
Copy the result, download a file, or jump into a related FreeTools.run utility (like Diff Checker or the QR Code Generator) to continue the workflow without leaving the browser.