The checker accepts the following parameters regardless of input method. How these parameters are communicated depends on the input method.

Note: The validator.nu deployment of the checker has a generic facet at https://validator.nu/ and an (X)HTML5 facet at https://html5.validator.nu/. Some parameters apply only to the generic facet. All parameters listed here are optional.

• none: HTML
• xhtml: XHTML
• xml: XML
• json: JSON
• gnu: GNU error format
• text: Human-readable text (not for machine parsing)

The only supported value is yes which means that source is shown (if supported by the output format).

The only supported value is error which means that only errors and non-document errors are reported. That is, informative messages including warnings are not reported.

Space-separated list of XML namespace URIs. Elements (and their children) and attributes in those namespaces are filtered out between the XML parser and the validation layer. The filtered elements participate in ID uniqueness checking. The filter doesn’t apply to HTML parser.

The only supported value is yes, which means that the checker will retrieve a document and check it even if the response from the server is a 404 or other non-200 status. Otherwise the checker will not retrieve the document but will instead emit a message indicating the document was not retrieved, along with the HTTP status code.

This parameter takes a space-separated list of schema IRIs (http or https). The schemas can be RELAX NG 1.0 schemas, Schematron 1.5 schemas or identifiers for built-in non-schema-based checkers.

The only supported value is yes which means that RFC 3023 character encoding defaults are disrespected and text/html is accepted as an XML MIME type.

These parameters are specific to only some output formats.

The only supported value is yes which means that ASCII quotes and apostrophes will be substituted for the Unicode smart quotes. This parameter only applies with out=text and out=gnu. The output may still contain Unicode characters in general.

When this parameter is present, its value is taken to be the name of a JavaScript callback function to which the JSON object is given as an argument. This parameter only applies with out=json. The value must not be a JavaScript reserved word.

See also: Web Service Interface