CourierAPI

Other mods call the CourierAPI Java API to queue a notification with a title, a description, a display duration and a set of ARGB colors for the background, border, accent and text. Each card slides in, stays for its configured time and slides out. Up to four cards are visible at once, and any further notifications wait in a queue that advances automatically. Descriptions that are too long wrap onto a second line.

Notifications can be broadcast from the server to connected clients, or shown locally by a client-only mod without any server involvement. Server owners who do not write code can place a couriernotifications.json file in the server root to define reusable notifications, then trigger them in-game with the courier command. This is useful for scheduled messages such as a restart warning, and external scripts can reach the same command through RCON. Using the command requires permission level 2, the operator level.

The mod is released under the MIT License and is open source. Players need it installed to see notifications, while a server can run without it, so either side may carry the mod and the server is not required to. Files are published only for Fabric, for game versions 1.21.11 – 26.1.2. The latest file, 26.1.2-0.1, was published on 2026-04-25.