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Update telemetry events documentation with PII warning #51284

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ManickaP merged 2 commits into from
Jan 22, 2026
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Update telemetry events documentation with PII warning #51284

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Update telemetry events documentation with PII warning
ManickaP Jan 22, 2026
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Update docs/fundamentals/networking/telemetry/events.md
ManickaP Jan 22, 2026
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8 changes: 7 additions & 1 deletion docs/fundamentals/networking/telemetry/events.md
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Expand Up @@ -288,14 +288,20 @@ You should think about such events separately. Monitor DNS resolutions or TLS ha
## Internal diagnostics

Some components in .NET are instrumented with additional debug-level events that provide more insight into exactly what's happening internally.
These events come with high performance overhead and their shape is constantly changing. As the name suggests, they are not part of the public API and you should therefore not rely on their behavior or existence.
These events come with high performance overhead and their shape is constantly changing. As the name suggests, they are not part of the public API and you should therefore not rely on their behavior or existence. Moreover, they are not redacted and might contain PII.

Regardless, these events can offer a lot of insights when all else fails.
The `System.Net` stack emits such events from `Private.InternalDiagnostics.System.Net.*` namespaces.

If you change the condition in the `EventListener` example above to `eventSource.Name.Contains("System.Net")`, you will see 100+ events from different layers in the stack.
For more information, see the [full example](https://github.com/dotnet/docs/tree/main/docs/fundamentals/networking/snippets/internal-diag-telemetry/Program.cs).

To consume them outside of the process, use `dotnet-trace`, for example:

```console
dotnet-trace collect --providers Private.InternalDiagnostics.System.Net.Http:0xf --process-id 1234
```

## Samples

- [Measure DNS resolutions for a given endpoint](#measure-dns-resolutions-for-a-given-endpoint)
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