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An extreme CSS reset stylesheet, for aggressively resetting the styling of an element and its children. Composed exclusively of CSS !important rules.
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Cleanslate is an extreme CSS reset stylesheet. It is used to reset the styling of an HTML element and all its children, back to default CSS values. It is composed exclusively of !important rules, which override all other types of rules.

It does not require any JavaScript – it’s just a CSS stylesheet. However, you may find it useful when used within JavaScript widgets, such as those created by Sqwidget.

If you have any feedback or questions, please raise an issue or contact @premasagar. Fork away.

License: Open source, MIT


  1. Include a <link> to cleanslate.css in the host page
  2. Add the class cleanslate to the HTML container element of the widget
  3. Add !important to all of the widget's CSS rules
  4. (optional) Set the default styles on the widget container

For more details, see 'Usage'.

Cleanslate is available on cdnjs, if you want the stylesheet already hosted.

Why would I need it?

Cleanslate is useful when there are existing CSS styles on a page, and you want to prevent those styles cascading into some part of the page. This is not a stylesheet to use when developing your own website (for that, try Eric Meyer’s classic Reset CSS or the HTML5 Doctors’ adaptation).

The stylesheet can be useful when distributing content (e.g. a widget, or syndicated news) to third-party websites. The CSS rules in the host site may be unknown and unpredictable, or may change in future without notice, or there may be so many websites you need to distribute to that it is impractical to write specific CSS that overrides the styles in each one. In such situations, the Cleanslate stylesheet will aggressively reset your portion of the content (and nothing else) back to some reasonable default values that you can then build from.

The stylesheet aims to list all standard HTML elements, and assigns them a default (or otherwise relevant) value for every CSS property. The stylesheet only targets elements that have a class attribute of "cleanslate" and their child elements.

Why not just use an iframe?

Third-party content is often distributed in iframes. Because JavaScript within an iframe can be prevented from accessing the host page, iframes are particularly useful when the host site has security concerns and does not explicitly trust the third-party content.

However, iframes have some drawbacks:

  • You cannot display content outside of the box of the iframe
  • It is tricky to resize the iframe to match the size of its contents
  • Your content will be unable to interact with the host page
  • Search engines like Google will not see the content on the host page. Content that is syndicated from a partner website can avoid this by being directly included in the host page.

[Edit]: The iframe's sandbox attribute that was added in HTML5 address a number of issues.

Pull requests

Pull requests are welcome.

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