Candidate Recommendation

CSS Speech Module

This specification defines aural CSS properties that enable authors to declaratively control the rendering of documents via speech synthesis. CSS (Cascading Style Sheets) is a language that describes the rendering of markup documents (e.g. HTML, XML) on various media, such as screen, paper, speech, etc.

Note: This Candidate Recommendation is a work in progress and may be updated, replaced or obsoleted by other documents at any time.

Table of contents


Introduction and Overview



Specifications typically include things like:

It might make sense to settle on a cannonical order for these things, and whether they are appendices or unlettered/unnumbered sections or what.

Status and Advancement

A Candidate Recommendation is a document that has been widely reviewed and is ready for implementation. W3C encourages everybody to implement this specification and send feedback to the Working Group as described above. Publication as a Candidate Recommendation does not imply endorsement by the W3C Membership.

Before the specification can progress to Proposed Recommendation, the CR exit criteria must be met. The specification will not become Proposed Recommendation before 20 September 2012. A test suite and an implementation report will be made during the Candidate Recommendation period.

The following features are at-risk and may be dropped at the end of the Candidate Recommendation period if there has not been enough interest from implementers: ‘voice-balance’, ‘voice-duration’, ‘voice-pitch’, ‘voice-range’, and ‘voice-stress’.

CR exit criteria

For this specification to be proposed as a W3C Recommendation, the following conditions shall be met. There must be at least two independent, interoperable implementations of each feature. Each feature may be implemented by a different set of products, there is no requirement that all features be implemented by a single product. For the purposes of this criterion, we define the following terms:

each implementation must be developed by a different party and cannot share, reuse, or derive from code used by another qualifying implementation. Sections of code that have no bearing on the implementation of this specification are exempt from this requirement.
passing the respective test case(s) in the official CSS test suite, or, if the implementation is not a Web browser, an equivalent test. Every relevant test in the test suite should have an equivalent test created if such a user agent (UA) is to be used to claim interoperability. In addition if such a UA is to be used to claim interoperability, then there must one or more additional UAs which can also pass those equivalent tests in the same way for the purpose of interoperability. The equivalent tests must be made publicly available for the purposes of peer review.
a user agent which:
  1. implements the specification.
  2. is available to the general public. The implementation may be a shipping product or other publicly available version (i.e., beta version, preview release, or "nightly build"). Non-shipping product releases must have implemented the feature(s) for a period of at least one month in order to demonstrate stability.
  3. is not experimental (i.e., a version specifically designed to pass the test suite and is not intended for normal usage going forward).

A minimum of sixth months of the CR period must have elapsed. This is to ensure that enough time is given for any remaining major errors to be caught.

Features will be dropped if two or more interoperable implementations are not found by the end of the CR period.

Features may/will also be dropped if adequate/sufficient (by judgment of CSS WG) tests have not been produced for those feature(s) by the end of the CR period.


This document was updated to address the issues listed in the Last Call Disposition Of Comments. Changes from the 18 August 2011 Last Call Working Draft include:

Copyrights and Licensing

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.


The editors would like to thank the members of the W3C Voice Browser and Cascading Style Sheets working groups for their assistance in preparing this specification. Special thanks to Ellen Eide (IBM) for her detailed comments, and to fantasai for her thorough reviews.