"keyids" Initialization Data Format W3C Group Note 04 June 2026 More details about this document This version: https://www.w3.org/TR/2026/NOTE-eme-initdata-keyids-20260604/ Latest published version: https://www.w3.org/TR/eme-initdata-keyids/ Latest editor's draft: https://w3c.github.io/encrypted-media/format-registry/initdata/keyids.html History: https://www.w3.org/standards/history/eme-initdata-keyids/ Commit history Editors: Xiaohan Wang ( Google Inc. ) Greg Freedman ( Netflix Inc. ) Former editors: Joey Parrish ( Google Inc. ) (Until June 2026) Mark Watson ( Netflix Inc. ) (Until September 2019) David Dorwin ( Google Inc. ) (Until September 2017) Jerry Smith ( Microsoft Corporation ) (Until September 2017) Adrian Bateman ( Microsoft Corporation ) (Until May 2014) Feedback: GitHub w3c/encrypted-media ( pull requests , new issue , open issues ) [email protected] with subject line [eme-initdata-keyids] … message topic … ( archives ) Copyright © 2026 World Wide Web Consortium . W3C ® liability , trademark and permissive document license rules apply. Abstract This specification defines the "keyids" initialization data format for use with the Encrypted Media Extensions [ ENCRYPTED-MEDIA ]. Note It defines a stream format-independent format for specifying a list of key ID (s). This type can be used by applications to directly provide information necessary to generate a license request without using media data or constructing container-specific formats. Status of This Document This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C standards and drafts index . This document was published by the Media Working Group as a Group Note using the Note track . This Group Note is endorsed by the Media Working Group , but is not endorsed by W3C itself nor its Members. The W3C Patent Policy does not carry any licensing requirements or commitments on this document. This document is governed by the 18 August 2025 W3C Process Document . Table of Contents Abstract Status of This Document 1. Format 2. Example 3. Conformance A. References A.1 Normative references 1. Format The format is a JSON object, encoded in UTF-8 as specified in the Encoding specification [ encoding ], containing the following member: "kids" An array of key ID (s). Each element of the array is the base64url encoding of the octet sequence containing the key ID value. Note See Using base64url . Note Applications may encode the JSON string using the TextEncoder interface [ encoding ]. 2. Example This section is non-normative. The following example will generate a license request for two key ID (s). (Line breaks are for readability only.) Example 1 { "kids" : [ "LwVHf8JLtPrv2GUXFW2v_A" , "0DdtU9od-Bh5L3xbv0Xf_A" ] } 3. Conformance As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative. A. References A.1 Normative references [encoding] Encoding Standard . Anne van Kesteren. WHATWG. Living Standard. URL: https://encoding.spec.whatwg.org/ [ENCRYPTED-MEDIA] Encrypted Media Extensions . Joey Parrish; Greg Freedman. W3C. 20 May 2026. W3C Working Draft. URL: https://www.w3.org/TR/encrypted-media-2/ ↑