URL filter API

By Opera Software

From Opera 15 onward, Opera 11 & 12’s extension format is no longer supported, and instead, we’ve switched to Chromium’s extension model. Check out our new documentation for developing extensions for Opera 15 and higher and start building your own extensions.

Adds a rule to the virtual list of blocked URLs.
Removes a rule from the virtual list of blocked URLs.
Adds a rule to the virtual list of allowed URLs.
Domains on which to not apply a filter rule.
Domains on which to apply a filter rule.
Resource types to apply a filter rule to.
Specifies whether a filter rule should apply to third-party domains.
URL Filter syntax
Special characters that can be used when filtering.


The URL Filter API for Opera extensions defines a DOM interface that allows extensions to add temporary rules to Opera's native content blocker. Rules added through this API are associated with an extension and apply as long as the extension is enabled. Once an extension is disabled or the browser is shut down, the temporary rules are discarded.

To enable the URL filter, the opera:urlfilter feature needs to be added as a feature element to the extension's config.xml file.

An in-depth tutorial is available at Dev.Opera: Site blocking with Opera's URL Filter API


Block example.com/images, example.com/css and any subdirectories, whatever the protocol. Note that www.example.com and other sub-domains are not affected.

  The configuration file ('config.xml').
<?xml version='1.0' encoding='utf-8'?>
<widget xmlns="http://www.w3.org/ns/widgets">
    <feature name="opera:urlfilter"/>
// The background process (e.g. index.html)

// Check that the URL Filter API exists
if (typeof opera.extension.urlfilter != 'undefined') {
  // Create a list of rules to block
  var rules = ['*://example.com/images/*', '*://example.com/css/*'];

  // Assign the URLFilter object to a variable for efficiency
  var filter = opera.extension.urlfilter;

  // Loop through the array of rules and add each one to the "block" list
  for (var i = 0, len = rules.length; i < len; i++) {

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    Thursday, May 10, 2012

    Do you plan to implement opera.extension.urlfilter.block.get() or opera.extension.urlfilter.block.list() method?

    Now extension should to keep the list of blocked urls in WebSQL DB, because there is no way to unlock URL if you don't know what exactly locked. One extension can add url to urlfilter and this url doesn't appears anywhere, not in urlfilter.ini, not in some other list.

    Am I correct?
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    Martin Kadlec

    Monday, July 30, 2012

    The documentation is missing some info about events or when script is blocked or not blocked because of white-list. The events are called: oncontentblocked and oncontentunblocked
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    Saturday, October 6, 2012

    Nice, so does this mean we could see improved adblock extensions closer to the quality of those found in chrome/firefox? I had been sticking with urlfilter.ini just because it seemed to work better than all the opera adblock extensions I tried.
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    Tuesday, November 27, 2012

    opera.extension.urlfilter.allow.remove() is also missing in the documentation.
    It does the same as block.remove but then for the Allow RuleList.
    You need it if you want to reset a RuleList entry
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