The W3C Widget Checker is a free service by W3C that helps check the validity of a widget package against the Widgets 1.0: Packaging and Configuration specification.
The service in an alpha version and only performs basic tests to assert the validity of a widget.
In addition to this checker, the W3C is offering a number of other tools to help you check various types of documents (HTML, XHTML, CSS, RDF, P3P, ...), find broken links in your Web pages, and so on. All these tools are listed on the W3C's QA Toolbox.
The W3C also hosts a number of other Open Source software projects.
The W3C Widget Checker uses the same checker framework as the W3C mobileOK Checker. It is thus based on an open source Java library developed within the Mobile Web Best Practices Working Group by the Checker Task Force.
The user interface of the W3C Widget Checker derives from that of the W3C mobileOK Checker.
The W3C Widget Checker is maintained by W3C staff.