Network Connectivity Status Indicator

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22 title: Network Connectivity Status Indicator overview for Windows

33 description: The Network Connectivity Status Indicator (NCSI) helps to detect network connectivity and troubleshoot via network probing and passive polling.

44 ms.topic: article

5 −ms.date: 06/23/2023

5 +ms.date: 02/25/2025

66 ms.author: alalve

77 author: xelu86

88 ms.contributors: rnitsch

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1111 # NCSI overview

1212

1313 > [!IMPORTANT]

14 −> The public NCSI probe servers formerly hosted by Azure Front Door are now being hosted by Akamai. This change occurred on June 20, 2023. To better understand how this affects users, see our [NCSI FAQ](ncsi-frequently-asked-questions.md) page.

14 +> Akamai now hosts the public NCSI probe servers, which Azure Front Door formerly hosted. This change occurred on June 20, 2023. To learn more about how this change impacts you, see the [NCSI FAQ](ncsi-frequently-asked-questions.md) page.

1515

16 −The Network Connectivity Status Indicator (NCSI) is a feature that helps to provide a visual display of the current network connection status. The NCSI icon is found on the bottom-right of the taskbar by default. Depending on how your device is connected to the network and what operating system you're running will determine its appearance.

16 +The Network Connectivity Status Indicator (NCSI) is a feature that helps to provide a visual display of the current network connection status. The NCSI icon is found on the bottom-right of the taskbar by default. Depending on how your device is connected to the network and what operating system is running determines its appearance.

1717

1818 |Icon|Description|

1919 |--|--|

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2525

2626 ## NCSI functionality

2727

28 −NCSI uses network probes that are network requests sent to an endpoint followed by a response. NCSI’s probe, referred to as an “active probe”, is an HTTP request/response. It also uses passive polling, referred to as "passive probe", which examines network traffic passively to determine connectivity.

28 +NCSI uses network probes that are network requests sent to an endpoint followed by a response. NCSI’s probe, referred to as an "active probe", is an HTTP request/response. It also uses passive polling, referred to as "passive probe", which examines network traffic passively to determine connectivity.

2929

3030 ### What is the purpose of NCSI in Windows?

3131

3232 NCSI is the component responsible for determining network connectivity exists and if it's Internet or local-only. The reason NCSI was developed to save applications the complex task of determining network configuration on its own. Every attempt to perform a task over the network would require constant attention to whether the network was still accessible. In a network outage, even intermittently, the application would time out the operation and tests the network continuously until the connection is stable.

3333

34 −This seems trivial until you consider that it must perform checks for a multitude of environmental factors such as being behind a proxy, hotspot, or captive portal. NCSI must know if the network it detects is one that can satisfy its requests. Does it need full internet or private corporate access? Users must wait for NCSI to either complete or time out while the application determines how to handle restrictive or no network connectivity scenarios.

34 +NCSI accounts for various environmental factors such as proxies, hotspots, or captive portals. It needs to determine if the detected network can fulfill its requests, whether it requires full internet access or private corporate access. Users must wait for NCSI to either complete its checks or time out while the application decides how to handle restrictive or no network connectivity scenarios.

3535

3636 ### Active probing

3737

38 −An active probe is an http request sent to a web probe server for a specific NCSI address. The server is hosted by Microsoft on the internet but can also be an enterprise’s own private probe server, which is a more uncommon scenario. When NCSI sends the probe and receives a valid response, it considers the client device to have internet connectivity.

38 +An active probe is an http request sent to a web probe server for a specific NCSI address. The server hosted by Microsoft on the internet but can also be an enterprise’s own private probe server, which is a more uncommon scenario. When NCSI sends the probe and receives a valid response, it considers the client device to have internet connectivity.

3939

4040 When NCSI doesn’t detect internet connectivity, it's either that the probe isn't completing, or the probe is completing with failure. Some reasons for not completing can be device, network configuration, or other environmental issues. An example of completing with a failure is receiving an **HTTP 403 Forbidden** response, usually indicating a proxy blocked the outbound probe.

4141

4242 > [!WARNING]

43 −> Do not disable active probing as a resolution to a NCSI issue as passive polling alone is unable to determine all network connectivity issues.

43 +> Don't disable active probing as a resolution to an NCSI issue as passive polling alone is unable to determine all network connectivity issues.

4444

4545 The HTTP probe hosts and contents are predefined and found in the following registry path:

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5252

5353 ### Passive probing

5454

55 −Similar to active probing, passive probing uses learned information from received packets to determine network status. Both probing methods complement one another as they determine intermittent network conditions differently. Certain conditions prevent active probes from functioning correctly, such as, a temporary router having intermittent connectivity issue where a client device doesn't experience any change in the interface state. In case of such intermittent connectivity issues, which can cause active probing to have false negative results, passive polling can determine the connectivity status due to network traffic and keep internet connectivity.

55 +Similar to active probing, passive probing uses learned information from received packets to determine network status. Both probing methods complement one another as they determine intermittent network conditions differently. Certain conditions prevent active probes from functioning correctly, such as, a temporary router having intermittent connectivity issue where a client device doesn't experience any change in the interface state. If intermittent connectivity issues cause active probing to have false negative results, passive polling can determine the connectivity status based on network traffic. This helps maintain accurate internet connectivity status.

5656

5757 > [!NOTE]

5858 > As of Windows 11, NCSI is hosted within the Network List Manager service, also known as the Network Profile Manager. Previous OS iterations were hosted in the Network Location Awareness (NLA) service.

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6767

6868 - A proxy exists but isn't yet discovered.

6969 - A proxy was discovered but the client device can't reach it at the time of the probe.

70 −- The Proxy Auto-Config (PAC) file is misconfigured and hasn't mapped `www.msftconnecttest.com` to the correct proxy.

70 +- The Proxy Auto-Config (PAC) file is misconfigured and didn't map `www.msftconnecttest.com` to the correct proxy.

7171 - The proxy is misconfigured.

7272

73 −NCSI will detect a manually provisioned proxy address from the following registry path:

73 +NCSI detects manually provisioned proxy address from the following registry path:

7474

7575 ```registry

7676 HKLM\SYSTEM\CurrentControlSet\Services\NlaSvc\Parameters\Internet\ManualProxies

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8181

8282 ### Captive portals

8383

84 −In the same way that NCSI detects proxies inside an enterprise in order to successfully navigate a probe to the internet, it also determines hindrances outside of an enterprise environment for consumers on mobile devices. Captive portals are largely found in public environments such as airports, hospitals, coffee shops, etc. but can also be gateways in satellite extensions of enterprise networks.

84 +NCSI detects proxies within an enterprise to successfully navigate a probe to the internet. It also identifies hindrances outside of an enterprise environment for consumers on mobile devices. Captive portals are largely found in public environments such as airports, hospitals, coffee shops, etc. but can also be gateways in satellite extensions of enterprise networks.

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86 −Captive portals may send an HTTP redirect or an empty response to the probe instead of allowing it through to the internet. This is how NCSI is able to determine if it’s behind a captive portal as long as the conditions below are true:

86 +Captive portals may send an HTTP redirect or an empty response to the probe instead of allowing it through to the internet. NCSI is able to determine if it’s behind a captive portal as long as the following conditions are true:

8787

8888 - An active HTTP probe was sent but not via a known proxy.

8989 - The probe got a response.

90 −- The response payload didn't match the expected content: “Microsoft Connect Test”.

90 +- The response payload didn't match the expected content: `Microsoft Connect Test`.

9191

92 −## Additional references

92 +## See also

9393

9494 - [NCSI Troubleshooting Guide](ncsi-troubleshooting-guide.md)

9595 - [NCSI FAQ](ncsi-frequently-asked-questions.md)

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