Table of contents

  1. 1 Introduction
  2. 2 Common infrastructure
  3. 3 Semantics, structure, and APIs of HTML documents
  4. 4 The elements of HTML
  5. 5 Microdata
  6. 6 User interaction
  7. 7 Loading web pages
  8. 8 Web application APIs
  9. 9 Communication
  10. 10 Web workers
  11. 11 Worklets
  12. 12 Web storage
  13. 13 The HTML syntax
  14. 14 The XML syntax
  15. 15 Rendering
  16. 16 Obsolete features
  17. 17 IANA considerations
  18. Index
  19. References
  20. Acknowledgments
  21. Intellectual property rights

Full table of contents

  1. 1 Introduction
    1. 1.1 Where does this specification fit?
    2. 1.2 Is this HTML5?
    3. 1.3 Background
    4. 1.4 Audience
    5. 1.5 Scope
    6. 1.6 History
    7. 1.7 Design notes
      1. 1.7.1 Serializability of script execution
      2. 1.7.2 Extensibility
    8. 1.8 HTML vs XML syntax
    9. 1.9 Structure of this specification
      1. 1.9.1 How to read this specification
      2. 1.9.2 Typographic conventions
    10. 1.10 A quick introduction to HTML
      1. 1.10.1 Writing secure applications with HTML
      2. 1.10.2 Common pitfalls to avoid when using the scripting APIs
      3. 1.10.3 How to catch mistakes when writing HTML: validators and conformance checkers
    11. 1.11 Conformance requirements for authors
      1. 1.11.1 Presentational markup
      2. 1.11.2 Syntax errors
      3. 1.11.3 Restrictions on content models and on attribute values
    12. 1.12 Suggested reading
  2. 2 Common infrastructure
    1. 2.1 Terminology
      1. 2.1.1 Parallelism
      2. 2.1.2 Resources
      3. 2.1.3 XML compatibility
      4. 2.1.4 DOM trees
      5. 2.1.5 Scripting
      6. 2.1.6 Plugins
      7. 2.1.7 Character encodings
      8. 2.1.8 Conformance classes
      9. 2.1.9 Dependencies
      10. 2.1.10 Extensibility
      11. 2.1.11 Interactions with XPath and XSLT
    2. 2.2 Policy-controlled features
    3. 2.3 Common microsyntaxes
      1. 2.3.1 Common parser idioms
      2. 2.3.2 Boolean attributes
      3. 2.3.3 Keywords and enumerated attributes
      4. 2.3.4 Numbers
        1. 2.3.4.1 Signed integers
        2. 2.3.4.2 Non-negative integers
        3. 2.3.4.3 Floating-point numbers
        4. 2.3.4.4 Percentages and lengths
        5. 2.3.4.5 Nonzero percentages and lengths
        6. 2.3.4.6 Lists of floating-point numbers
        7. 2.3.4.7 Lists of dimensions
      5. 2.3.5 Dates and times
        1. 2.3.5.1 Months
        2. 2.3.5.2 Dates
        3. 2.3.5.3 Yearless dates
        4. 2.3.5.4 Times
        5. 2.3.5.5 Local dates and times
        6. 2.3.5.6 Time zones
        7. 2.3.5.7 Global dates and times
        8. 2.3.5.8 Weeks
        9. 2.3.5.9 Durations
        10. 2.3.5.10 Vaguer moments in time
      6. 2.3.6 Legacy colors
      7. 2.3.7 Space-separated tokens
      8. 2.3.8 Comma-separated tokens
      9. 2.3.9 References
      10. 2.3.10 Media queries
      11. 2.3.11 Unique internal values
    4. 2.4 URLs
      1. 2.4.1 Terminology
      2. 2.4.2 Parsing URLs
      3. 2.4.3 Document base URLs
    5. 2.5 Fetching resources
      1. 2.5.1 Terminology
      2. 2.5.2 Determining the type of a resource
      3. 2.5.3 Extracting character encodings from meta elements
      4. 2.5.4 CORS settings attributes
      5. 2.5.5 Referrer policy attributes
      6. 2.5.6 Nonce attributes
      7. 2.5.7 Lazy loading attributes
      8. 2.5.8 Blocking attributes
      9. 2.5.9 Fetch priority attributes
    6. 2.6 Common DOM interfaces
      1. 2.6.1 Reflecting content attributes in IDL attributes
      2. 2.6.2 Using reflect via IDL extended attributes
      3. 2.6.3 Using reflect in specifications
      4. 2.6.4 Collections
        1. 2.6.4.1 The HTMLAllCollection interface
          1. 2.6.4.1.1 [[Call]] ( thisArgument, argumentsList )
        2. 2.6.4.2 The HTMLFormControlsCollection interface
        3. 2.6.4.3 The HTMLOptionsCollection interface
      5. 2.6.5 The DOMStringList interface
    7. 2.7 Safe passing of structured data
      1. 2.7.1 Serializable objects
      2. 2.7.2 Transferable objects
      3. 2.7.3 StructuredSerializeInternal ( value, forStorage [ , memory ] )
      4. 2.7.4 StructuredSerialize ( value )
      5. 2.7.5 StructuredSerializeForStorage ( value )
      6. 2.7.6 StructuredDeserialize ( serialized, targetRealm [ , memory ] )
      7. 2.7.7 StructuredSerializeWithTransfer ( value, transferList )
      8. 2.7.8 StructuredDeserializeWithTransfer ( serializeWithTransferResult, targetRealm )
      9. 2.7.9 Performing serialization and transferring from other specifications
      10. 2.7.10 Structured cloning API
  3. 3 Semantics, structure, and APIs of HTML documents
    1. 3.1 Documents
      1. 3.1.1 The Document object
      2. 3.1.2 The DocumentOrShadowRoot interface
      3. 3.1.3 Resource metadata management
      4. 3.1.4 Reporting document loading status
      5. 3.1.5 Render-blocking mechanism
      6. 3.1.6 DOM tree accessors
    2. 3.2 Elements
      1. 3.2.1 Semantics
      2. 3.2.2 Elements in the DOM
      3. 3.2.3 HTML element constructors
      4. 3.2.4 Element definitions
        1. 3.2.4.1 Attributes
      5. 3.2.5 Content models
        1. 3.2.5.1 The "nothing" content model
        2. 3.2.5.2 Kinds of content
          1. 3.2.5.2.1 Metadata content
          2. 3.2.5.2.2 Flow content
          3. 3.2.5.2.3 Sectioning content
          4. 3.2.5.2.4 Heading content
          5. 3.2.5.2.5 Phrasing content
          6. 3.2.5.2.6 Embedded content
          7. 3.2.5.2.7 Interactive content
          8. 3.2.5.2.8 Palpable content
          9. 3.2.5.2.9 Script-supporting elements
          10. 3.2.5.2.10 select element inner content elements
          11. 3.2.5.2.11 optgroup element inner content elements
          12. 3.2.5.2.12 option element inner content elements
        3. 3.2.5.3 Transparent content models
        4. 3.2.5.4 Paragraphs
      6. 3.2.6 Global attributes
        1. 3.2.6.1 The title attribute
        2. 3.2.6.2 The lang and xml:lang attributes
        3. 3.2.6.3 The translate attribute
        4. 3.2.6.4 The dir attribute
        5. 3.2.6.5 The style attribute
        6. 3.2.6.6 Embedding custom non-visible data with the data-* attributes
      7. 3.2.7 The innerText and outerText properties
      8. 3.2.8 Requirements relating to the bidirectional algorithm
        1. 3.2.8.1 Authoring conformance criteria for bidirectional-algorithm formatting characters
        2. 3.2.8.2 User agent conformance criteria
      9. 3.2.9 Requirements related to ARIA and to platform accessibility APIs
  4. 4 The elements of HTML
    1. 4.1 The document element
      1. 4.1.1 The html element
    2. 4.2 Document metadata
      1. 4.2.1 The head element
      2. 4.2.2 The title element
      3. 4.2.3 The base element
      4. 4.2.4 The link element
        1. 4.2.4.1 Processing the media attribute
        2. 4.2.4.2 Processing the type attribute
        3. 4.2.4.3 Fetching and processing a resource from a link element
        4. 4.2.4.4 Processing `Link` headers
        5. 4.2.4.5 Early hints
        6. 4.2.4.6 Providing users with a means to follow hyperlinks created using the link element
      5. 4.2.5 The meta element
        1. 4.2.5.1 Standard metadata names
        2. 4.2.5.2 Other metadata names
        3. 4.2.5.3 Pragma directives
        4. 4.2.5.4 Specifying the document's character encoding
      6. 4.2.6 The style element
      7. 4.2.7 Interactions of styling and scripting
    3. 4.3 Sections
      1. 4.3.1 The body element
      2. 4.3.2 The article element
      3. 4.3.3 The section element
      4. 4.3.4 The nav element
      5. 4.3.5 The aside element
      6. 4.3.6 The h1, h2, h3, h4, h5, and h6 elements
      7. 4.3.7 The hgroup element
      8. 4.3.8 The header element
      9. 4.3.9 The footer element
      10. 4.3.10 The address element
      11. 4.3.11 Headings and outlines
        1. 4.3.11.1 Sample outlines
        2. 4.3.11.2 Exposing outlines to users
      12. 4.3.12 Usage summary
        1. 4.3.12.1 Article or section?
    4. 4.4 Grouping content
      1. 4.4.1 The p element
      2. 4.4.2 The hr element
      3. 4.4.3 The pre element
      4. 4.4.4 The blockquote element
      5. 4.4.5 The ol element
      6. 4.4.6 The ul element
      7. 4.4.7 The menu element
      8. 4.4.8 The li element
      9. 4.4.9 The dl element
      10. 4.4.10 The dt element
      11. 4.4.11 The dd element
      12. 4.4.12 The figure element
      13. 4.4.13 The figcaption element
      14. 4.4.14 The main element
      15. 4.4.15 The search element
      16. 4.4.16 The div element
    5. 4.5 Text-level semantics
      1. 4.5.1 The a element
      2. 4.5.2 The em element
      3. 4.5.3 The strong element
      4. 4.5.4 The small element
      5. 4.5.5 The s element
      6. 4.5.6 The cite element
      7. 4.5.7 The q element
      8. 4.5.8 The dfn element
      9. 4.5.9 The abbr element
      10. 4.5.10 The ruby element
      11. 4.5.11 The rt element
      12. 4.5.12 The rp element
      13. 4.5.13 The data element
      14. 4.5.14 The time element
      15. 4.5.15 The code element
      16. 4.5.16 The var element
      17. 4.5.17 The samp element
      18. 4.5.18 The kbd element
      19. 4.5.19 The sub and sup elements
      20. 4.5.20 The i element
      21. 4.5.21 The b element
      22. 4.5.22 The u element
      23. 4.5.23 The mark element
      24. 4.5.24 The bdi element
      25. 4.5.25 The bdo element
      26. 4.5.26 The span element
      27. 4.5.27 The br element
      28. 4.5.28 The wbr element
      29. 4.5.29 Usage summary
    6. 4.6 Links
      1. 4.6.1 Introduction
      2. 4.6.2 Links created by a and area elements
      3. 4.6.3 API for a and area elements
      4. 4.6.4 Following hyperlinks
      5. 4.6.5 Downloading resources
      6. 4.6.6 Hyperlink auditing
        1. 4.6.6.1 The `Ping-From` and `Ping-To` headers
      7. 4.6.7 Link types
        1. 4.6.7.1 Link type "alternate"
        2. 4.6.7.2 Link type "author"
        3. 4.6.7.3 Link type "bookmark"
        4. 4.6.7.4 Link type "canonical"
        5. 4.6.7.5 Link type "dns-prefetch"
        6. 4.6.7.6 Link type "expect"
        7. 4.6.7.7 Link type "external"
        8. 4.6.7.8 Link type "help"
        9. 4.6.7.9 Link type "icon"
        10. 4.6.7.10 Link type "license"
        11. 4.6.7.11 Link type "manifest"
        12. 4.6.7.12 Link type "modulepreload"
        13. 4.6.7.13 Link type "nofollow"
        14. 4.6.7.14 Link type "noopener"
        15. 4.6.7.15 Link type "noreferrer"
        16. 4.6.7.16 Link type "opener"
        17. 4.6.7.17 Link type "pingback"
        18. 4.6.7.18 Link type "preconnect"
        19. 4.6.7.19 Link type "prefetch"
        20. 4.6.7.20 Link type "preload"
        21. 4.6.7.21 Link type "privacy-policy"
        22. 4.6.7.22 Link type "search"
        23. 4.6.7.23 Link type "stylesheet"
        24. 4.6.7.24 Link type "tag"
        25. 4.6.7.25 Link Type "terms-of-service"
        26. 4.6.7.26 Sequential link types
          1. 4.6.7.26.1 Link type "next"
          2. 4.6.7.26.2 Link type "prev"
        27. 4.6.7.27 Other link types
    7. 4.7 Edits
      1. 4.7.1 The ins element
      2. 4.7.2 The del element
      3. 4.7.3 Attributes common to ins and del elements
      4. 4.7.4 Edits and paragraphs
      5. 4.7.5 Edits and lists
      6. 4.7.6 Edits and tables
    8. 4.8 Embedded content
      1. 4.8.1 The picture element
      2. 4.8.2 The source element
      3. 4.8.3 The img element
      4. 4.8.4 Images
        1. 4.8.4.1 Introduction
          1. 4.8.4.1.1 Adaptive images
        2. 4.8.4.2 Attributes common to source, img, and link elements
          1. 4.8.4.2.1 Srcset attributes
          2. 4.8.4.2.2 Sizes attributes
        3. 4.8.4.3 Processing model
          1. 4.8.4.3.1 When to obtain images
          2. 4.8.4.3.2 Reacting to DOM mutations
          3. 4.8.4.3.3 The list of available images
          4. 4.8.4.3.4 Decoding images
          5. 4.8.4.3.5 Updating the image data
          6. 4.8.4.3.6 Preparing an image for presentation
          7. 4.8.4.3.7 Selecting an image source
          8. 4.8.4.3.8 Creating a source set from attributes
          9. 4.8.4.3.9 Updating the source set
          10. 4.8.4.3.10 Parsing a srcset attribute
          11. 4.8.4.3.11 Parsing a sizes attribute
          12. 4.8.4.3.12 Normalizing the source densities
          13. 4.8.4.3.13 Reacting to environment changes
        4. 4.8.4.4 Requirements for providing text to act as an alternative for images
          1. 4.8.4.4.1 General guidelines
          2. 4.8.4.4.2 A link or button containing nothing but the image
          3. 4.8.4.4.3 A phrase or paragraph with an alternative graphical representation: charts, diagrams, graphs, maps, illustrations
          4. 4.8.4.4.4 A short phrase or label with an alternative graphical representation: icons, logos
          5. 4.8.4.4.5 Text that has been rendered to a graphic for typographical effect
          6. 4.8.4.4.6 A graphical representation of some of the surrounding text
          7. 4.8.4.4.7 Ancillary images
          8. 4.8.4.4.8 A purely decorative image that doesn't add any information
          9. 4.8.4.4.9 A group of images that form a single larger picture with no links
          10. 4.8.4.4.10 A group of images that form a single larger picture with links
          11. 4.8.4.4.11 A key part of the content
          12. 4.8.4.4.12 An image not intended for the user
          13. 4.8.4.4.13 An image in an email or private document intended for a specific person who is known to be able to view images
          14. 4.8.4.4.14 Guidance for markup generators
          15. 4.8.4.4.15 Guidance for conformance checkers
      5. 4.8.5 The iframe element
      6. 4.8.6 The embed element
      7. 4.8.7 The object element
      8. 4.8.8 The video element
      9. 4.8.9 The audio element
      10. 4.8.10 The track element
      11. 4.8.11 Media elements
        1. 4.8.11.1 Error codes
        2. 4.8.11.2 Location of the media resource
        3. 4.8.11.3 MIME types
        4. 4.8.11.4 Network states
        5. 4.8.11.5 Loading the media resource
        6. 4.8.11.6 Offsets into the media resource
        7. 4.8.11.7 Ready states
        8. 4.8.11.8 Playing the media resource
        9. 4.8.11.9 Seeking
        10. 4.8.11.10 Media resources with multiple media tracks
          1. 4.8.11.10.1 AudioTrackList and VideoTrackList objects
          2. 4.8.11.10.2 Selecting specific audio and video tracks declaratively
        11. 4.8.11.11 Timed text tracks
          1. 4.8.11.11.1 Text track model
          2. 4.8.11.11.2 Sourcing in-band text tracks
          3. 4.8.11.11.3 Sourcing out-of-band text tracks
          4. 4.8.11.11.4 Guidelines for exposing cues in various formats as text track cues
          5. 4.8.11.11.5 Text track API
          6. 4.8.11.11.6 Event handlers for objects of the text track APIs
          7. 4.8.11.11.7 Best practices for metadata text tracks
        12. 4.8.11.12 Identifying a track kind through a URL
        13. 4.8.11.13 User interface
        14. 4.8.11.14 Time ranges
        15. 4.8.11.15 The TrackEvent interface
        16. 4.8.11.16 Events summary
        17. 4.8.11.17 Security and privacy considerations
        18. 4.8.11.18 Best practices for authors using media elements
        19. 4.8.11.19 Best practices for implementers of media elements
      12. 4.8.12 The map element
      13. 4.8.13 The area element
      14. 4.8.14 Image maps
        1. 4.8.14.1 Authoring
        2. 4.8.14.2 Processing model
      15. 4.8.15 MathML
      16. 4.8.16 SVG
      17. 4.8.17 Dimension attributes
    9. 4.9 Tabular data
      1. 4.9.1 The table element
        1. 4.9.1.1 Techniques for describing tables
        2. 4.9.1.2 Techniques for table design
      2. 4.9.2 The caption element
      3. 4.9.3 The colgroup element
      4. 4.9.4 The col element
      5. 4.9.5 The tbody element
      6. 4.9.6 The thead element
      7. 4.9.7 The tfoot element
      8. 4.9.8 The tr element
      9. 4.9.9 The td element
      10. 4.9.10 The th element
      11. 4.9.11 Attributes common to td and th elements
      12. 4.9.12 Processing model
        1. 4.9.12.1 Forming a table
        2. 4.9.12.2 Forming relationships between data cells and header cells
      13. 4.9.13 Examples