Rec. ITU-T T.808 | ISO/IEC 15444-9 provides a network protocol that allows for the interactive and progressive transmission of JPEG 2000 coded data and files from a server to a client. The 1st edition of this Recommendation | International Standard dates to 2005. It has since then been supplemented by amendments and corrigenda. Additionally, other members of the JPEG 2000 family of Recommendations | International Standards, that are capable of being used with the network protocol described in this Recommendation | International Standard have since been introduced. The second edition incorporated the changes associated with these developments, without modifying the original scope. This third edition extends the set of supported underlying transport protocols to include HTTP/3. This Recommendation was developed jointly with ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information, and is common text with ISO/IEC 15444-9. This third edition cancels and replaces the second edition, which has been technically revised. The main changes compared to the previous edition are as follows: 1. this edition specifies methods for HTTP/3 transported JPIP communication (Annex P); and 2. this edition adds the H3 and H3S transport types to the definition of the New Channel request and response fields. This Recommendation contains an electronic attachment that is to be available from the ITU website at: https://www.itu.int/ifa/t/2025/sg21/exchange/AAP/T.808v3/ when published, and from the ISO website at: https://standards.iso.org/iso-iec/15444/-9/ed-3/en. This third edition cancels and replaces the second edition, which has been technically revised. The main changes compared to the previous edition are as follows – this version: consolidates all outstanding amendments and corrigenda published since the first edition; extends support for the file format specified in Rec. ITU-T T.815 | ISO/IEC 15444-16; clarifies normative server responsibilities in response to certain request fields documented in Annex C; removes the registration authority (Annex L); and adds media type registration information (Annex O).