The following are a list of extension specifications that are actively being developed. Some of these may be integrated during the Candidate Recommdation phase of HTML 5.0, others may integrate later, and some may proceed independently indefinitely.
Want to write one? Read How to Write an Extension Specification.
- Encrypted Media Extensions
- Media Source Extensions
- The srcset attribute - Use Cases
- The picture Element - Use Cases
- Public Identifiers for entity resolution in XHTML
- Form HTTP Extensions - Rationale
- Polyglot Markup: A robust profile of the HTML5 vocabulary – an extension spec that defines the common, DOM-equal and most robust subset of HTML and XHTML.
- HTML JSON form submission - This specification defines a new form encoding algorithm that enables the transmission of form data as JSON.
Web Application Security WG
- <main> - Rationale and use cases was folded into the HTML specification.
- HTML Ruby Markup Extensions was folded back into the HTML specification