This setting, SitePerProcess, may be used to disallow users from opting out of the default behavior of isolating all sites. Note that the IsolateOrigins policy may also be useful for isolating additional, finer-grained origins.
If the policy is enabled, users will be unable to opt out of the default behavior where each site runs in its own process.
If the policy is not configured or disabled, the user will be able to opt out of site isolation
(e.g. using "Disable site isolation" entry in chrome://flags). Setting the policy to disabled and/or not configuring the policy does not turn off Site Isolation.
On Google Chrome OS version 76 and earlier, it is recommended to also set the DeviceLoginScreenSitePerProcess device policy to the same value. If the values specified by the two policies don't match, a delay may be incurred when entering a user session while the value specified by user policy is being applied.
NOTE: This policy does not apply on Android. To enable SitePerProcess on Android, use the SitePerProcessAndroid policy setting.