Available rules

Rules with are enabled by htmlvalidate:recommended.
Rules with are enabled by htmlvalidate:document.

button-type Require button to have valid type
close-attr Disallow end tags from having attributes
close-order Require elements to be closed in correct order
deprecated Disallow usage of deprecated elements
element-name Disallow invalid element names
no-conditional-comment Disallow usage of conditional comments
no-deprecated-attr Disallow usage of deprecated attributes
no-dup-attr Disallow duplicated attributes
no-dup-class Disallow duplicated classes
no-dup-id Disallow duplicated IDs

Content model

attribute-allowed-values Validate permitted attribute values
element-permitted-content Validate permitted content from content model
element-permitted-occurrences Validate permitted number of occurrences from content model
element-permitted-order Validate required order from content model

Accessibility

img-req-alt Require img to have alt attribute
input-missing-label Require input to have label

Style

attr-case Require a specific case for attribute names
attr-quotes Require attribute quoting
class-pattern Require classes to match a specific pattern
element-case Require a specific case for element names
id-pattern Require IDs to match a specific pattern
no-implicit-close Require elements with optional end tags to be explicitly closed
no-inline-style Disallow inline style
no-trailing-whitespace Disallow trailing whitespace
void Disallow void element with content

Document

These rules is to be used on full documents.

heading-level Require headings to start at h1 and be sequential
missing-doctype Require document to have a doctype