# Internals

Here is a quick overview of the most important code parts. They can be found in the telemetry folder.

- TelemetryController: Main telemetry logic, e.g. assembling pings, local storage (when archiving is enabled), preference changes, testing
- Telemetry.cpp contains most of the public interface, implements the IDL
- The different data types for telemetry are handled in TelemetryHistogram, TelemetryScalar, TelemetryEvent.
- TelemetryEnvironment: A helper for gathering environment data, like build version or graphics data
- TelemetryScheduler: Starts regular jobs for collecting and sending data
- TelemetrySend: Sending and caching of pings
- TelemetryStorage: Handles writing pings to disk for TelemetrySend
- TelemetrySession: Collects data for a browsing session, includes many of the most important probes (aka metrics)
- Policy: A layer of indirection added to provide testability. A common pattern in many files
- pings/: Contains definitions and handling for most ping types, like EventPing

More details on different topics can be found in these chapters:

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