Certificate authority (CA) A certificate authority is an entity similar to a notary public. It issues digital certificates, signs certificates to verify their validity and tracks which certificates have been revoked or have expired. Top of Page Digital signature assurances The following terms and definitions show what assurances are provided by digital signatures. Authenticity The signer is ...

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Troubleshoot slow game or app downloads on Xbox One Account error occurs when signing in to Xbox network

Activation helps verify that your copy of Windows is genuine and hasn’t been used on more devices than the Microsoft Software License Terms allow. There are two methods to which you can activate your product: Online via the internet, and by using the Product Activation Portal. Online: When you begin activation, Windows will try to use your internet connection to activate online. If you have ...

Signing in connects the apps to the rest of Microsoft 365, letting you save files to the cloud, share files with others, and have your documents save automatically as you work.

The default authentication method is to use the free Microsoft Authenticator app. If you have it installed on your mobile device, select Next and follow the prompts to add this account.

Learn how to sign in and create app passwords for Microsoft apps and devices that don't support two-step verification.

Learn how you can use the free Microsoft Authenticator app to sign in to all your accounts without using a password.

Several Microsoft 365 apps have versions available for Windows Mobile, iOS, and Android devices. For more information about the apps, see Microsoft 365 for Mobile.

Microsoft Teams 網頁版應用程式適用於大部分的桌面瀏覽器，包含了 Chrome、Firefox 和 Internet Explorer。