At the time SMART App Launch was standardized, there was no convention established. See discussion at https://oauth.ietf.narkive.com/9TbUoMUV/oauth-wg-standard-url-parameter-for-mitigating-rfc6819-s-threat-4-6-4  which resulted in the recommendation to name the parameter "aud" – note this is from 2015, and practices have evolved since! Drafted in 2018 an eventually finalized in 2020, https://datatracker.ietf.org/doc/rfc8707/  standardizes a parameter called "resource". We could update the SMART spec to deprecated "aud" and declare "resource" as a new name; but changing this would break SMART client compatibility across the board, so it's unclear when/how we could finalize the deprecation, meaning that servers would be on the hook for managing "aud" and "resource" parameters indefinitely. Update the spec to add a note at the end of the "aud" parameter definition:   > Note that the "aud" parameter is semantically equivalent to the   "resource" parameter defined in [RFC8707] ( https://datatracker.ietf.org/doc/rfc8707 ). SMART's, "aud" parameter predates RFC8707 and we have decided not to rename it for reasons of backwards compatibility. We might consider renaming SMART's "aud" parameter in the future if implementer feedback indicates that alignment would be valuable. For the current release, servers SHALL support the "aud" parameter and MAY support a "resource" parameter as a synonym for "aud".