A *license* is a usage agreement between you and a software vendor. To use
licensed software provided by Google Cloud, you must have a license. For
example, if you are running a licensed operating system (OS) on a Compute Engine virtual machine (VM) instance, you must have a license for that
OS.

A *license string* is a resource that associates a usage agreement with a
licensed OS, OS upgrade, or additional software. For a list of the license
strings that are associated with each OS that is supported by Compute Engine,
see [Operating system details](https://docs.cloud.google.com/compute/docs/images/os-details#license-strings).
To learn how to view and manage license strings, see
[Manage licenses](https://docs.cloud.google.com/compute/docs/licenses/manage).

## License types and pricing

Licenses on Compute Engine are one of the following types. For
information about which license types apply to each OS version, see the
*license* section of the
[Operating system details](https://docs.cloud.google.com/compute/docs/images/os-details#license-strings) page.

Free licenses
:   No charge for usage.

On-demand/Pay-as-you-go (PAYG)

:   Google Cloud charges for usage. Cost varies depending on the OS. For
    more information, see [pricing for premium images](https://docs.cloud.google.com/compute/disks-image-pricing#premiumimages).

:   The Google-provided image contains enhancements that might not be included if you bring your own
    OS image.

Bring your own license (BYOL)/Bring your own subscription (BYOS)

:   Google Cloud does not charge you because you have a previous agreement
    with the original OS vendor. If you have BYOL licenses for server or client
    versions of Windows, you must use [sole-tenant nodes](https://docs.cloud.google.com/compute/docs/nodes/sole-tenant-nodes).

:   License strings for BYOL and BYOS end with `byol` or `byos`. If the license
    string does not end with `byol` or `byos`, the license is a free or
    on-demand/PAYG license.

    For more information about using BYOS and BYOL licenses on Compute Engine,
    review the following:

    - For RHEL BYOS, see [Create a VM using a RHEL BYOS image](https://docs.cloud.google.com/compute/docs/instances/create-rhel-byos-vm).
    - For Windows, contact your [Google Cloud Technical Account Manager](https://docs.cloud.google.com/support/docs/premium#tam).

Upgrade from Ubuntu to Ubuntu Pro

:   The following Ubuntu versions have reached the end of maintenance:

    - Ubuntu 16.04 LTS - April 21, 2021
    - Ubuntu 18.04 LTS - May 31, 2023

    If you need further updates for these versions, you must upgrade and append
    a user license for Ubuntu Pro. For information about how to upgrade and append
    a user license,
    see [Upgrade from Ubuntu to Ubuntu Pro](https://docs.cloud.google.com/compute/docs/images/premium/ubuntu-pro/upgrade-from-ubuntu).

Use SQL Server on Linux

:   You can install SQL Server on Linux VMs and use PAYG licenses. For more
    information, see [Add a SQL Server license to an existing Linux server](https://docs.cloud.google.com/compute/docs/instances/sql-server/adding-sql-server-license-to-linux).

## What's next

- [Manage licenses](https://docs.cloud.google.com/compute/docs/licenses/manage)

- [Learn about Microsoft licenses on Compute Engine](https://docs.cloud.google.com/compute/docs/instances/windows/ms-licensing)

- Learn more about premium operating systems:

  - [Consult the RHEL FAQ](https://docs.cloud.google.com/compute/docs/images/premium/rhel-faq)

  - [Consult the Ubuntu Pro FAQ](https://docs.cloud.google.com/compute/docs/images/premium/ubuntu-pro-faq)

- Review [Support policy by license type](https://docs.cloud.google.com/compute/docs/images/support-maintenance-policy#support-by-license)