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# Matter Constants

## Topics

### Constants

[`let MTRDataVersionKey: String`](/documentation/Matter/MTRDataVersionKey)

[`let MTREventIsHistoricalKey: String`](/documentation/Matter/MTREventIsHistoricalKey)

[`let MTRPreviousDataKey: String`](/documentation/Matter/MTRPreviousDataKey)

[`var MTR_ENABLE_PROVISIONAL: Int32`](/documentation/Matter/MTR_ENABLE_PROVISIONAL)

[`var MTR_ENABLE_UNSTABLE_API: Int32`](/documentation/Matter/MTR_ENABLE_UNSTABLE_API)

[`var MTR_NO_AVAILABILITY: Int32`](/documentation/Matter/MTR_NO_AVAILABILITY)


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