You can see what devices are connected to your Gmail account by accessing your account security settings. Go to myaccount.google.com, click "Security" in the left menu, then scroll to "Your devices" and select "Manage all devices." This shows all devices where you're currently signed in to Google services, including phones, tablets, and computers.
For more detailed activity, visit the "Your activity" section where you can see recent sign-in locations and access times. You can also check "Manage your Google Account" > "Security" > "Recent security events" to see login attempts from different locations and devices.
If you notice unfamiliar devices, you can remotely sign out by selecting the device and clicking "Sign out." For added security, consider enabling two-step verification, which requires a second form of authentication beyond your password. This helps prevent unauthorized access even if someone obtains your password.
You can also review connected apps and websites that have access to your account under "Security" > "Third-party apps & services." Remove access from any apps you no longer recognize or use. Regularly reviewing these settings helps ensure only your trusted devices and applications can access your Gmail account.