mikaela.github.io/n/matrixspoilers.md

The Matrix specification supports spoilers since version 1.1:

• Spoiler messages at Client-Server API of Matrix Specification

My favourite Matrix clients FluffyChat and Nheko support spoilers when the spoiler is formatted like ||Reason why this is a spoiler|Actually spoilered text.|| It can be in-line and reasonless spoilers are just ||spoiler goes here||.

Element Web supports whole message spoilers through the /spoiler command. I am not sure on other Elements as I barely use them for other things than /devtools command.

Other clients supporting formatting such as Nheko older than 60b1a595e121e6d824cab188abac750be4459058 will have to enter the HTML directly such as:

<span data-mx-spoiler="REASON HERE">Spoilered text</span>

Nheko has a /plain command to disable formatting for that message which allows sending this message in plain text to help someone else.

/plain <span data-mx-spoiler="REASON HERE">Spoilered text</span>

Spoilers are also supported by IRC, but not matrix-appservice-irc.

• matrix-org/matrix-appservice-irc#1548: Feature request: bridge spoilers to IRC by sending them with the same background&foreground colour (and that to Matrix as spoiler)