MSBuild Visual Studio Telemetry Data

This document describes the telemetry data collected by MSBuild and sent to Visual Studio telemetry infrastructure. The telemetry helps the MSBuild team understand build patterns, identify issues, and improve the build experience.

Overview

MSBuild collects telemetry at multiple levels:

1. Build-level telemetry - Overall build metrics and outcomes
2. Task-level telemetry - Information about task execution
3. Target-level telemetry - Information about target execution and incrementality
4. Error categorization telemetry - Classification of build failures

All telemetry events use the VS/MSBuild/ prefix as required by VS exporting/collection. Properties use the VS.MSBuild. prefix.

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1. Build Telemetry (build event)

The primary telemetry event capturing overall build information.

Properties

Property	Type	Description
BuildDurationInMilliseconds	double	Total build duration from start to finish
InnerBuildDurationInMilliseconds	double	Duration from when BuildManager starts (excludes server connection time)
BuildEngineHost	string	Host environment: "VS", "VSCode", "Azure DevOps", "GitHub Action", "CLI", etc.
BuildSuccess	bool	Whether the build succeeded
BuildTarget	string	The target(s) being built
BuildEngineVersion	Version	MSBuild engine version
BuildEngineDisplayVersion	string	Display-friendly engine version
BuildEngineFrameworkName	string	Runtime framework name
BuildCheckEnabled	bool	Whether BuildCheck (static analysis) was enabled
MultiThreadedModeEnabled	bool	Whether multi-threaded build mode was enabled
SACEnabled	bool	Whether Smart Application Control was enabled
IsStandaloneExecution	bool	True if MSBuild runs from command line
InitialMSBuildServerState	string	Server state before build: "cold", "hot", or null
ServerFallbackReason	string	If server was bypassed: "ServerBusy", "ConnectionError", or null
ProjectPath	string	Path to the project file being built
FailureCategory	string	Primary failure category when build fails (see Error Categorization)
ErrorCounts	object	Breakdown of errors by category (see Error Categorization)

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2. Error Categorization

When a build fails, errors are categorized to help identify the source of failures.

Error Categories

Category	Error Code Prefixes	Description
Compiler	CS, FS, VBC	C#, F#, and Visual Basic compiler errors
MsBuildGeneral	MSB4001-MSB4099, MSB4500-MSB4999	General MSBuild errors
MsBuildEvaluation	MSB4100-MSB4199	Project evaluation errors
MsBuildExecution	MSB4300-MSB4399, MSB5xxx-MSB6xxx	Build execution errors
MsBuildGraph	MSB4400-MSB4499	Static graph build errors
Task	MSB3xxx	Task-related errors
SdkResolvers	MSB4200-MSB4299	SDK resolution errors
NetSdk	NETSDK	.NET SDK errors
NuGet	NU	NuGet package errors
BuildCheck	BC	BuildCheck rule violations
NativeToolchain	LNK, C1xxx-C4xxx, CL	Native C/C++ toolchain errors (linker, compiler)
CodeAnalysis	CA, IDE	Code analysis and IDE analyzer errors
Razor	RZ	Razor compilation errors
Wpf	XC, MC	WPF/XAML compilation errors
AspNet	ASP, BL	ASP.NET and Blazor errors
Other	(all others)	Uncategorized errors

3. Task Telemetry

Task Factory Event (build/tasks/taskfactory)

Tracks which task factories are being used.

Property	Type	Description
AssemblyTaskFactoryTasksExecutedCount	int	Tasks loaded via AssemblyTaskFactory
IntrinsicTaskFactoryTasksExecutedCount	int	Built-in intrinsic tasks
CodeTaskFactoryTasksExecutedCount	int	Tasks created via CodeTaskFactory
RoslynCodeTaskFactoryTasksExecutedCount	int	Tasks created via RoslynCodeTaskFactory
XamlTaskFactoryTasksExecutedCount	int	Tasks created via XamlTaskFactory
CustomTaskFactoryTasksExecutedCount	int	Tasks from custom task factories

4. Build Incrementality Telemetry

Classifies builds as full or incremental based on target execution patterns.

Incrementality Info (Activity Property)

Field	Type	Description
Classification	enum	Full, Incremental, or Unknown
TotalTargetsCount	int	Total number of targets
ExecutedTargetsCount	int	Targets that ran
SkippedTargetsCount	int	Targets that were skipped
SkippedDueToUpToDateCount	int	Skipped because outputs were current
SkippedDueToConditionCount	int	Skipped due to false condition
SkippedDueToPreviouslyBuiltCount	int	Skipped because already built
IncrementalityRatio	double	Ratio of skipped to total (0.0-1.0)

A build is classified as Incremental when more than 70% of targets are skipped.

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Privacy Considerations

Data Hashing

Custom and potentially sensitive data is hashed using SHA-256 before being sent:

• Custom task names - Hashed to protect proprietary task names
• Custom target names - Hashed to protect proprietary target names
• Custom task factory names - Hashed if not in the known list
• Metaproj target names - Hashed to protect solution structure

Known Task Factory Names (Not Hashed)

The following Microsoft-owned task factory names are sent in plain text:

• AssemblyTaskFactory
• TaskHostFactory
• CodeTaskFactory
• RoslynCodeTaskFactory
• XamlTaskFactory
• IntrinsicTaskFactory

Related Files

File	Description
BuildTelemetry.cs	Main build telemetry class
BuildInsights.cs	Container for detailed insights
TelemetryDataUtils.cs	Data transformation utilities
BuildErrorTelemetryTracker.cs	Error categorization
ProjectTelemetry.cs	Per-project task telemetry
LoggingConfigurationTelemetry.cs	Logger configuration
BuildCheckTelemetry.cs	BuildCheck telemetry
KnownTelemetry.cs	Static telemetry accessors
TelemetryConstants.cs	Telemetry naming constants