Both ChatGPT and Claude have a Log out of all devices control that ends every open session at once. Docognito is a separate tool for the session you choose to keep open afterward, since it disguises the page rather than the account behind it. Both controls sit under Settings, Security.
Where the setting lives on each assistant
Both platforms keep this option in the same general area, under a settings section named Security or Sessions, rather than buried in a general preferences page.
On ChatGPT, open Settings, then Security, where an Active sessions or similar list shows every device currently signed in, with a single control to log out everywhere. On Claude, open Settings, then Security, which carries the equivalent Active sessions view and its own log out control. Neither assistant hides this behind a support ticket or a password reset flow. It is a normal, self service setting.
What ending every session actually does
Choosing this option invalidates the sign in tokens tied to your account across every browser and app currently using them. The practical result is that any device that was signed in, whether that is a work laptop, a shared family computer, or your phone, gets logged out and has to sign in again the next time someone opens the app.
This is different from changing a password. A password change on its own sometimes leaves existing sessions active until they expire naturally. A dedicated log out control is the more direct route when the goal is ending access right now, on every device at once.
How to confirm it actually worked
Once you have triggered the log out, it is worth checking rather than assuming. Return to the same Security page a minute or two later and look at the active session list again. On both assistants, only the device you are currently using should still appear there, since it is the one signing back in as you view the page. Any other device that was previously listed should be gone, and the next time that device is opened it should prompt for a password rather than loading straight into an existing session.
ChatGPT can take up to thirty minutes to actually close a session everywhere
ChatGPT documents a delay of up to thirty minutes before an active session on another device is fully closed after you trigger a log out. If a shared computer is still logged in during that window, treat it as not yet secure rather than assuming the click was instant.
Steps to sign out everywhere on each assistant
Open Security settings
On ChatGPT, go to Settings, then Security. On Claude, go to Settings, then Security. Both list your active sessions on this page.
Review the active session list
Check the devices and browsers shown before you act, particularly if the reason you came here is a session you do not recognise.
Log out of all devices
Confirm the log out control. Every session ends at once, and each device asks for your credentials again the next time it opens the app.
Why this is not the same job as Docognito
Logging out and disguising a page solve two entirely different problems, and it is worth keeping them apart in your head. A log out ends the account's access on every device. Docognito changes the visible page, redrawn as a document editor, the the browser tab title and the the tab icon on the tab that stays open, so that a glance at your screen reads as a document rather than a chat. Turning the disguise on or off has no bearing on whether any session stays signed in, and signing out everywhere has no bearing on how the page looks while you are still using it.
When this is the setting you actually want
Reach for a full log out when you have used your account on a computer you do not control, when a device was lost or is no longer in your possession, or when a session in the active list looks unfamiliar. It is a security action aimed at access, not a visual one aimed at what a passerby sees on your own screen right now.
A shared or work computer is a common trigger for this, since it is the one situation where you have both used your account somewhere you do not fully control and want a clean way to close that out afterward. Making a habit of checking the active session list occasionally, even without a specific reason, costs little and catches an account that was left signed in somewhere you had forgotten about.
Closing old access and hiding the current session are different jobs
Closing access on devices you are no longer using means going to Settings, Security on either assistant and logging out of all devices, then allowing for ChatGPT's short delay before treating the job as finished. If the goal is keeping the session you are actively using from announcing itself on screen, that is a separate job. Use each assistant's own security page for the first, and Docognito for the second.