About

The Iframe Source Viewer (more accurately, a Compatibility & Embed Tool) addresses a critical challenge in modern web development: Cross-Origin Restrictions. While the Same-Origin Policy prevents direct inspection of external source code via JavaScript, this tool provides a comprehensive environment to test renderability and generate production-ready HTML.

Many major platforms enforce X-Frame-Options: DENY or Content-Security-Policy headers to prevent clickjacking. This utility allows you to simulate how a URL behaves inside a sandboxed container before deploying it. It includes precise viewport controls to test responsiveness across mobile, tablet, and desktop breakpoints without leaving your browser.

Formulas

The generated embed code follows the standard HTML5 specification combined with modern CSS for responsiveness.

{

AspectRatio = HeightWidth × 100%Padding-Bottom Technique

When Responsive Mode is active, we utilize a container wrapper to maintain the aspect ratio:

.wrapperposition: relative;padding-bottom: 56.25%;height: 0;

Reference Data

Attribute / Header	Type	Impact & Description
src	URL	The source address. Must be HTTPS for most modern contexts to avoid Mixed Content errors.
sandbox	Security	Enables extra restrictions. Empty value forbids all. Tokens like allow-scripts lift specific bans.
loading	Performance	Values: lazy (defer load until viewport) or eager (load immediately). Critical for Core Web Vitals.
X-Frame-Options	Header	Server-side header. If set to DENY or SAMEORIGIN, the browser will refuse to render the content.
allow	Feature Policy	Controls access to device features like camera, microphone, or geolocation.

Frequently Asked Questions

This indicates the target website has set an "X-Frame-Options" or "Content-Security-Policy" header to strictly forbid embedding. This is a security feature to prevent Clickjacking. You cannot bypass this client-side.

Lazy loading ('loading="lazy"') tells the browser to pause downloading the iframe content until the user scrolls near it. This significantly improves initial page load speed (LCP). Eager loading downloads it immediately.

Adding the "sandbox" attribute without flags applies maximum security (no scripts, no forms, no popups). Checking flags like "allow-scripts" selectively re-enables these features while keeping others blocked.

Not directly via HTML alone due to Cross-Origin (SOP) rules. The parent page cannot read the height of the child page unless you use a library like "iframe-resizer" that requires scripts running on BOTH the parent and the child pages.