HTML srcdoc Attribute: Reference and Examples

The srcdoc attribute is a small instruction attached to an HTML element. Its job is to inline HTML document to display inside iframe. It is easier to remember when you can see it in a real piece of markup.

What srcdoc is used for

Inline HTML document to display inside iframe. The attribute appears inside an element’s opening tag. Depending on its definition, it may take a specific string, a number, an enumerated keyword, or be a boolean attribute.

The example below uses it in a iframe context. Other elements may support it too, or may give the same attribute a different meaning.

Example you can try

<section>
    <iframe title="Greeting preview" srcdoc="&lt;p&gt;Hello from iframe&lt;/p&gt;" sandbox></iframe>
</section>

How the example works

Look for srcdoc in the snippet. Here the example shows the value <p>Hello from iframe</p>. This is a concrete input the browser can interpret; it is not just text shown to the reader.

Never concatenate untrusted user input into srcdoc without a trustworthy sanitization/security strategy.

Values and important behavior

Use the value format shown by the HTML definition. Do not assume that a value accepted in one attribute also works in another. When a browser ignores an invalid value, inspect the element and correct the markup.

This detail matters most when the page receives user input, navigates to another document, or loads an external resource. In those cases, check the browser behavior and any server-side requirements separately.

Small practice task

Copy the code and change srcdoc to another sensible value, or remove it entirely if it is optional. Test the difference in the browser and inspect any submitted value or network request.

Common Beginner Mistakes

• Never concatenate untrusted user input into srcdoc without a trustworthy sanitization/security strategy.
• Using srcdoc on an element that does not support it.
• Believing that an HTML hint or client-side check replaces real server validation or a security policy.

Key Takeaways

• srcdoc is used to inline HTML document to display inside iframe.
• Never concatenate untrusted user input into srcdoc without a trustworthy sanitization/security strategy.
• Choose valid values and test the result instead of guessing what the browser will do.