The company said when it announced the policy that it was for security reasons: Accounts that have not been used for a long time are more likely to be compromised. It also said that idle accounts were 10 times less likely to have two-factor verification, which checks a user’s identity.

The policy applies only to personal accounts, not those managed by a business or school.

Google said certain accounts would be exempt from deletion, even if they were inactive for two years, including those that contained a gift card with a monetary balance or had an active paid subscription.

Although the company said it could begin purging accounts on Dec. 1, it may not eliminate all of them immediately. Google said in May that it planned to start with accounts that had never been used.

If a Google account is deleted, all of its content and data may disappear. Before beginning deletion, Google said it would warn users in multiple emails to the inactive Google account and to another email, if one has been saved to a user’s account.