Managing Windows Delivery Optimization to prevent sluggish online performance

Users experiencing slow internet on Windows PCs may find that Delivery Optimization, which shares update files across devices, is the hidden culprit. Learning to control this feature can ensure smoother online experiences.

If a Windows PC feels sluggish online despite a fast broadband connection, the culprit may be Windows itself. Microsoft’s Delivery Optimization system can both fetch update files from other computers and send them onwards from your machine, according to Microsoft Support, while Tom’s Guide warns that the background traffic can be most noticeable during gaming, video calls and streaming.

That matters because the feature is broader than a simple Windows Update download. Microsoft says Delivery Optimization can source Windows updates and Microsoft Store apps from other PCs on a local network or on the wider internet, depending on how it is configured. Microsoft Learn adds that the same mechanism is used for a wider set of content, including Defender definition updates, Edge browser updates, Microsoft 365 apps and some Xbox Game Pass downloads. If peers or a local cache are unavailable, the system falls back to an ordinary HTTP download, so the feature is meant as an efficiency layer rather than a mandatory replacement for Microsoft’s servers.

Microsoft’s own documentation also makes clear that the behaviour is controllable. In Windows 11, the route is Settings > Windows Update > Advanced options > Delivery Optimization. From there, users can switch sharing to “Devices on my local network” or turn the option off entirely. Tom’s Guide argues that the middle setting is often the most practical compromise for households with several Windows PCs, because it keeps update sharing inside the home while stopping uploads to the wider internet. The same report recommends using the Advanced options page to cap upload bandwidth to about 5-10% if you want to keep some peer sharing without letting it interfere with calls or online play. Microsoft adds another useful safeguard: on a metered or capped connection, Delivery Optimization will not automatically download or send update parts to other PCs on the internet.

The debate around this setting is not new. PCWorld highlighted the same behaviour during the Windows 10 era, when the feature was presented as a peer-to-peer way of spreading updates and, by default at the time, could send and receive files from both the local network and the wider internet. Microsoft’s current enterprise documentation presents a narrower default for modern client editions, saying peer-to-peer sharing is enabled by default on the local network behind the same NAT in Enterprise, Professional and Education editions, with broader behaviour left to policy settings. That distinction matters in 2026 because Microsoft Support now explicitly notes that Windows 10 support ended on October 14, 2025, so users still on that platform may be dealing with an older interface and different documentation for a system that no longer receives free security updates.

Microsoft also disputes the idea that Delivery Optimization is inherently unsafe. Its support notes say the service cannot access personal files or folders and cannot be used to transfer personal content. Instead, update packages are split into smaller parts, checked against Microsoft’s authenticity information and verified again before installation. Microsoft Learn frames the technology in the same way, as a bandwidth-saving and reliability tool for homes, businesses and managed fleets using products such as Windows Server Update Services, Intune and Configuration Manager.

For traffic that does not come from Windows Update, built-in controls are less comprehensive. That is where third-party firewalls enter the picture. Safing describes Portmaster as a “free and open-source application firewall” that monitors every network connection on a computer and applies rules per application. According to the company, users can cut an app off from the internet entirely, block specific connection types or apply restrictions globally or on a per-app basis, including country-based limits.

Independent product coverage suggests Portmaster goes further than a simple on-off switch. Softpedia’s current Windows listing says version 2.2.3 was updated on August 21, 2026, has a 96.8MB installer and supports Windows 11 and Windows 10 64-bit. Its review says clicking a running program shows up to 10 minutes of connection history, including the domains contacted, and allows rules covering internet, LAN, direct and incoming connections. Softpedia also notes trade-offs in the free edition: no Network History, no Bandwidth Visibility and no Weekly Reports. Even so, that still makes it a more granular tool than Windows’ standard settings for users trying to identify which applications are quietly talking to the network.

The practical lesson is that “slow internet” on a Windows PC is often a traffic-management problem rather than a DNS problem or a router fault. Delivery Optimization can be useful, particularly on a home network with several Windows machines, but it should be set deliberately rather than left unexplored. Restricting it to the local network, applying modest upload caps and using a per-application firewall where necessary is a more precise response than blanket tweaking. Microsoft’s own documents show the feature was designed to save bandwidth overall; the problem for consumers is that the wrong setting can make their own connection feel as though it is being spent somewhere else.