DevCoreTools
Web Tools

HTML Previewer

Write or paste HTML and preview the rendered result instantly in your browser using an isolated preview frame.

HTML preview guide

HTML input

Edit a snippet, component, or complete HTML document.

Processed locally in your browser. Limit 5 MB Your input is processed in your browser and is not uploaded or sent to a server. Avoid pasting production secrets, access tokens, private keys, passwords, or sensitive customer data unless you understand the risk.
Scripts stay blockedJavaScript, inline handlers, forms, popups, same-origin access, and top navigation are never enabled.

Live preview

Rendered in a sandboxed, opaque-origin iframe.

Ready to preview HTML

Paste HTML or load a sample to render it inside the isolated preview frame.

Scripts and external resources are blocked by default. Press Ctrl+Enter or Command+Enter to refresh.

HTML Preview Guide

Preview HTML in an isolated browser frame

Use the live preview to inspect layout and styling while keeping untrusted markup separate from the DevCoreTools application.

What is an HTML Previewer?

An HTML previewer renders markup as a browser page so you can review structure, typography, spacing, forms, tables, and component layouts while editing.

How live HTML preview works

Your input becomes an iframe srcdoc document. Auto-preview can refresh after edits, or you can pause it and use the refresh action on demand.

HTML Previewer vs HTML Formatter

The previewer renders markup visually. The HTML Formatter changes source indentation and highlights structural issues without executing or rendering the result.

Safe iframe preview limitations

The frame has no same-origin access, form submission, popups, or top navigation. Some browser APIs and integrations will not behave like a deployed page.

Why scripts are blocked by default

HTML can contain scripts and inline event handlers. Blocking them prevents unexpected code execution until you deliberately opt into the restricted script sandbox.

Previewing snippets vs full HTML pages

Fragments are accepted and the browser supplies the document wrapper. Full pages can include a doctype, head metadata, embedded styles, and body content.

HTML Previewer FAQ

Does this HTML previewer upload my HTML?

No. Preview generation, warnings, copy, and download actions run locally in your browser.

Does it execute JavaScript?

No. Scripts and inline event handlers remain blocked in every preview.

Why is the preview sandboxed?

The sandbox separates untrusted markup from the Angular application and restricts capabilities that could navigate, submit, open windows, or access the parent page.

Can I preview full HTML pages?

Yes. Full documents and partial snippets are both supported, although deployment-specific server behavior and browser permissions are outside the preview.

Can external images or CSS load in the preview?

External resources are blocked by default. Enabling them may contact the hosts referenced by your HTML, so review URLs before opting in.

What is the difference between HTML Previewer and HTML Formatter?

The previewer shows rendered output. The formatter rewrites HTML source for readability and keeps all markup inert.

Keep working

HTML Formatter / BeautifierFormat and beautify HTML locally with indentation and structural warnings.HTML MinifierMinify HTML locally with conservative whitespace, comment, and template-preservation options.
CSS FormatterComing soon
Format CSS stylesheets with consistent indentation.
JavaScript FormatterFormat and beautify JavaScript locally with syntax validation and configurable style options.HTML Entity Encoder/DecoderEncode and decode HTML entities, symbols, and special characters locally.XML FormatterFormat, beautify, validate, copy, and download XML locally.
URL Encoder/DecoderComing soon
Encode and decode URL components and query-string values.