A shim for the iFrame "srcdoc" attribute

Usage no npm install needed!

<script type="module">
  import srcdocPolyfill from '';


srcdoc polyfill Build Status

HTML5 defines a new attribute for iFrames namedsrcdoc. This attribute allows developers to specify an iFrame's content in-line with the iFrame itself. For instance:

<iframe srcdoc="<html><body>Hello, <b>world</b>.</body></html>"></iframe>

This feature only began to see adoption in major browsers in early 2013. Fortunately, most older browsers support similar functionality through script-targeted URLs, i.e.

<iframe src="javascript: '<html><body>Hello, <b>world</b>.</body></html>'"></iframe>

(Because of limitations on URL length, the actual mechanism that the polyfill implements not quite this direct.)

For more on srcdoc, see the WhatWG specification and this post on


By including the script at the bottom of the document <body>, any available iFrames which declare a srcdoc attribute attribute) will receive this "shimmed" behavior. (In browsers that already implement this functionality, no change will take place.)

Note on the HTML5 sandbox attribute: Because the shim operates using a script-targeted URL in legacy environments, some configurations of the sandbox attribute may interfere with its behavior. This issue will only surface in environments that implement sandbox but that do not implement srcdoc. Because of this, this polyfill's default behavior is to issue a warning for potentially-hazardous configurations but to proceed optimistically. The API supports an force option that enables modification of this behavior.


This script may be consumed as a AMD module, a CommonJS module, or standalone via direct inclusion with a <script> element.


The shim also defines a minimal JavaScript API:

  • srcDoc.set( iframe [, content [, options ] ] ) - sets the content of the provided iFrame element using the srcdoc attribute where available (falling back on a script-targeted URL in non-supporting browsers).
    • content (optional) - The desired content of the iFrame. If blank, the current value of the element's srcdoc attribute will be referenced for content.
    • options (optional) - An object used to specify low-level behavior. Supports a single attribute, force, for controlling behavior in the presence of the sandbox attribute (see the note in "Usage" section of this document).
      • If unspecified, a warning will be issued and the library will attempt to shim the srcdoc behavior optimistically.
      • If true, then the target iFrame's sandbox attribute will be removed prior to setting the content. Note that this
      • If false, no warning will be issued and the library will attempt to shim the srcdoc behavior optimistically.
  • srcDoc.noConflict() - Sets the value of the global srcDoc variable to its original value. Returns the srcDoc object defined by this project for re-aliasing.

Browser Support

Tested in the following browsers:

  • Microsoft Internet Explorer
    • 6, 7, 8, 9, 10, 11
  • Microsoft Edge
    • 13, 14
  • Apple Safari
    • 4, 5.0, 5.1, 6, 6.2, 7.1, 8, 9.1, 10
  • Google Chrome
    • 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24.0.1312.5 (beta), 25.0.1364.5 (dev), 55
  • Opera
    • 11.1, 11.5, 11.6, 12.10, 12.11 (beta), 42
  • Mozilla FireFox
    • 3.0, 3.6, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 (beta), 50

The following browsers are not supported:

  • Opera 10.0


The build process for this project is written with Grunt.js. Please refer to the grunt documentation for details on installing grunt.


The shim's tests are written in QUnit, and can be run by visiting the test/index.html file in the browser, or by running grunt test from the command line.

Release Notes

  • 1.0.0 (2017-01-29)
    • Warn in the presence of the sandbox attribute if its value may cause issues in environments that support it
  • 0.2.0 (2015-10-02)
    • Wrap in "UMD" pattern, enabling more natural consumption from CommonJS and AMD environments
  • 0.1.1 (2013-03-01)
    • Allow content length to exceed the limit browsers impose on URLs
  • 0.1.0 (2012-06-13)
    • Initial release


Copyright (c) 2012 Mike Pennisi
Licensed under the MIT license.