Subscribe to Slots

Slot subscriptions provide real-time updates about Solana’s slot progression. This is essential for understanding chain state, tracking confirmations, and synchronizing your application with the blockchain.

Overview

A slot represents a period of time (400ms) during which a leader can produce a block. Slot subscriptions notify you as slots progress through different states:

• When a slot is first created
• When a slot becomes frozen (no more transactions can be added)
• When a slot reaches different commitment levels
• Parent-child relationships between slots

Filter Structure

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message SubscribeRequestFilterSlots {
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    optional bool filter_by_commitment = 1;
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    optional bool interslot_updates = 2;
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}

Filter Options

Filter by Commitment

Control whether to receive updates only for specific commitment levels.

Field: filter_by_commitment
Type: bool
Default: false

When false:

• Receive updates for all slot state changes
• Most comprehensive view of chain progression

When true:

• Only receive updates matching the commitment level specified in the main SubscribeRequest
• Reduces update volume
• Useful when you only care about confirmed or finalized slots

Interslot Updates

Control whether to receive updates during slot progression (before slot completion).

Field: interslot_updates
Type: optional bool
Default: false

When true:

• Receive multiple updates as slot progresses through different states
• More granular view of slot lifecycle
• Higher update volume

When false:

• Receive updates only at major slot state transitions
• Lower update volume

Response Structure

Slot updates arrive as SubscribeUpdateSlot messages:

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message SubscribeUpdateSlot {
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    uint64 slot = 1;
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    optional uint64 parent = 2;
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    SlotStatus status = 3;
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    optional string dead_error = 4;
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}
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enum SlotStatus {
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    SLOT_PROCESSED = 0;
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    SLOT_CONFIRMED = 1;
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    SLOT_FINALIZED = 2;
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    SLOT_FIRST_SHRED_RECEIVED = 3;
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    SLOT_COMPLETED = 4;
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    SLOT_CREATED_BANK = 5;
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    SLOT_DEAD = 6;
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}

Fields

slot: The slot number
parent: Parent slot number (optional)
status: Current status of the slot (see SlotStatus enum)
dead_error: If present, error message indicating why the slot is dead/skipped

Slot Status Values

SLOT_PROCESSED (0): Slot has been processed by the validator
SLOT_CONFIRMED (1): Slot has received supermajority confirmation
SLOT_FINALIZED (2): Slot is finalized and cannot be rolled back
SLOT_FIRST_SHRED_RECEIVED (3): First shred (data fragment) of the slot received
SLOT_COMPLETED (4): Slot has been completed
SLOT_CREATED_BANK (5): Bank (account state) created for this slot
SLOT_DEAD (6): Slot has been marked as dead/skipped