1SE closes on its own, freezes, or won't open? On iPhone and Android, most crashes come down to four things, in order:
Is the app actually up to date?
Updates roll out gradually. On iPhone, open the App Store app (not 1SE), tap your profile picture, and look for 1SE under pending updates; if it isn't there, search for "1 Second Everyday" and tap Update if its page offers it. On Android, open the Play Store, tap your profile picture, then Manage apps & device. Otherwise, see why the store may not offer you the update.
Is your phone's software recent enough?
1SE 6.3 and later need iOS 18. Update iOS first (Settings > General > Software Update), then 1SE. On Android, 1SE needs Android 11 or later.
Is there enough free space?
Keep at least 5–10 GB free; if you're below that, free some space and try again. What the "Disk space is very low" error means.
Still crashing? Send us your logs
Open 1SE right after a crash and follow How to Send Us Your Logs, with a line about what you were doing. We'll take it from there.