Download Mode

Purpose

Show registry keys (1)

• HKLM\SOFTWARE\Policies\Microsoft\Windows\DeliveryOptimization\DODownloadMode

This machine-wide REG_DWORD value determines which sources Windows Delivery Optimization may use to obtain supported content for Microsoft products. Depending on the value, Delivery Optimization can use the original HTTP source, Microsoft Connected Cache, and/or peer devices.

Value	Effect
0	Uses HTTP sources or Microsoft Connected Cache, but no peers. The Delivery Optimization cloud service can still provide metadata.
1	Combines HTTP sources with peers that use the same public IP address or NAT connection. The actual peer communication occurs within the network.
2	Combines HTTP sources with peers in the same private group. The group can span internal subnets and NAT boundaries; its membership depends in part on the Group ID and Group ID source settings.
3	Combines HTTP sources with internet peers.
99	Uses only HTTP sources or Microsoft Connected Cache. Peering and communication with the Delivery Optimization cloud service are disabled. This Simple mode is intended for environments without internet access to the cloud service.
100	Bypasses Delivery Optimization and transfers downloads to the Background Intelligent Transfer Service (BITS). This mode is deprecated starting with Windows 11.

When peers and Microsoft Connected Cache are available, Delivery Optimization can use multiple sources in parallel. If content cannot be obtained from those sources, the original HTTP source remains available as a fallback.

Notes

Additional effects

In modes 1, 2, and 3, the device can upload eligible cached Microsoft content to other peers. The value establishes the general scope of the peer group. Other policies can further restrict peer selection, group formation, bandwidth usage, and the conditions under which uploads are permitted.

This setting controls the sources used by Delivery Optimization and the scope of content sharing. It does not prevent Windows Update, Microsoft Store, or other integrated services from downloading their content.

Security

Peer transfers use the Delivery Optimization protocol over TCP port 7680, not SMB shares or general file access. Delivery Optimization does not access or share personal files and folders.

Content pieces received from peers are initially treated as untrusted. Windows validates each piece against cryptographically protected content metadata and discards invalid data. Allowing peers therefore does not grant those devices general access to files or other system resources.

The modes nevertheless differ in network exposure: mode 1 limits peering to devices behind the same public IP address, mode 2 can form private groups across subnet and NAT boundaries, and mode 3 permits internet peers. Membership in the same Microsoft Entra tenant, Active Directory site or domain, or Delivery Optimization group must not be treated as authentication of participating devices.

Possible side effects

Peer-enabled modes generate upload traffic in addition to downloads and require extra peer communication. They can reduce traffic from internet content sources, but consume local network, disk, and device resources. Actual usage depends on peer availability, supported content types, and other applicable policies.

Modes 0 and 99 disable peering. This removes the ability to reuse cached content from peer devices, so multiple devices might retrieve the same content more often from an HTTP source or Microsoft Connected Cache.

With value 100, content that requires Delivery Optimization can fail to download; Microsoft documents error 0x80d03002 as one possible result. The value is deprecated on Windows 11.

Notes

Value 0 disables only peer-to-peer transfers, not the Delivery Optimization HTTP downloader. Value 99 also disables communication with the Delivery Optimization cloud service.

Microsoft documentation

Microsoft Learn: Policy CSP – DeliveryOptimization (DODownloadMode)

Microsoft Learn: Delivery Optimization reference – Download Mode

Microsoft Learn: How Delivery Optimization works

Microsoft Learn: Delivery Optimization Frequently Asked Questions

See also

• Entry in the reference