24 hours
A message expires 24 hours after it is sent. Toward the end the text fades and photos blur, so you know what is coming. An expired message is gone from our database too: there is no archive behind the app.
Keep, when you both want it
Press and hold a message and mark it Keep. When the other person marks it too, it stays for good, outlined in gold. One of you wanting it is not enough.
In a group, a message stays when at least half of the members keep it.
Photos, clips, voice and files
Media fades out after 24 hours even in a message kept with Keep, because Keep holds the message, not the file. To keep it:
Flatline
If a chat reaches 0 BPM, messages that are not kept are deleted after 48 hours. See A chat's pulse.