> For the complete documentation index, see [llms.txt](https://developer.barchart.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.barchart.com/getting-started/data-flow.md).

# Data Flow

Choose how Openfeed delivers your subscribed market data.

Openfeed delivers market data after it accepts a subscription. The initial messages establish instrument state. Later messages deliver updates for the selected subscription types.

### Symbol subscription flow

For a symbol subscription with `TRADES` only, Openfeed sends messages in this order:

1. `subscriptionResponse` confirms the subscription and assigns its channel.
2. `instrumentDefinition` provides the instrument metadata and price formats.
3. `marketSnapshot` provides the complete current market state.
4. `trade` messages provide incremental trade updates.

The snapshot establishes the initial state. Apply each incremental update afterward to keep local state current.

### Delivery options

Use [Streaming Service Types](/getting-started/service-types.md) for continuous real-time or delayed updates. Use [Streaming Snapshot Types](/getting-started/service-types/streaming-snapshot-types.md) for periodic market snapshots.

Confirm your permissions in [User Settings](/openfeed-api/user-settings.md) before subscribing.


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