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

1 message SubscribeRequestFilterSlots {
2     optional bool filter_by_commitment = 1;
3     optional bool interslot_updates = 2;
4 }

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:

1 message SubscribeUpdateSlot {
2     uint64 slot = 1;
3     optional uint64 parent = 2;
4     SlotStatus status = 3;
5     optional string dead_error = 4;
6 }
7 
8 enum SlotStatus {
9     SLOT_PROCESSED = 0;
10     SLOT_CONFIRMED = 1;
11     SLOT_FINALIZED = 2;
12     SLOT_FIRST_SHRED_RECEIVED = 3;
13     SLOT_COMPLETED = 4;
14     SLOT_CREATED_BANK = 5;
15     SLOT_DEAD = 6;
16 }

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