Concepts

Message

A "message" is a single timestamped log entry, which can be sent to the Foxglove app or written to an MCAP file.

Schemas

A "schema" describes the structure of a message's contents.

Foxglove defines several message types with visualization support. You may also define your own schemas using one of many supported encodings.

For information about how to define your own schemas and log different types of messages, see Logging Messages.

Channels

A "channel" gives a way to log related messages which have the same schema. Each channel is identified by a unique topic name.

For Foxglove messages, the SDK provides type-safe channels for logging messages with a known, matching schema.

You may log your own custom data by defining channels with your schemas and logging messages to them. See the quickstart example.

Sinks

A "sink" is a destination for logged messages. A WebSocket client is a sink, as is an MCAP writer. If you do not configure a sink, log messages will simply be dropped without being recorded. You can configure multiple sinks, and you can create or destroy them dynamically at runtime.

See the quickstart example for basic usage.

MCAP

MCAP is a container file format for multimodal log data, supported by Foxglove.