UID
A UID is the unique identifier assigned to each participant position in a Bittensor subnet. Each miner or validator registered to a subnet holds a UID that identifies their position within that subnet’s participant set (Glossary: UID slot, Understanding Subnets).
UID is identifier vocabulary. It names the number, not the position structure itself. UID slot is the related term for the participant position that the UID identifies.
Subnet-Specific Scope
UIDs are subnet-specific. The same UID number can appear in different subnets while referring to different participants. A UID identifies a position within one subnet’s participant set, not a network-wide identity (Understanding Subnets).
Netuid identifies the subnet itself, while UID identifies a participant within that subnet (Glossary: Netuid). The two terms answer different questions about the same subnet context.
Registration and UIDs
A participant receives a UID by registering to a subnet. Registration assigns a UID to a hotkey, placing that participant into a UID slot within the subnet’s capacity (Glossary: Register).
That means a UID is earned through registration, not self-assigned. If the subnet is at capacity, registration replaces the lowest-ranked existing participant through the immunity and deregistration rules.
Metagraph Context
The metagraph records each subnet’s participant set. UIDs appear in metagraph data as identifiers for the miners and validators indexed in that subnet’s state (Glossary: Metagraph).
Reading a UID from metagraph data gives a position identifier within the subnet’s current participant set. The position’s associated state — stake, rank, trust — is indexed by that UID.
Development Stage Context
The Introduction to Bittensor describes subnet development as moving from localnet to testnet and then mainnet. For UIDs, that sequence changes which subnet participant set a reader should assume when matching a UID to a miner or validator.
In localnet, UID assignment can be tested through isolated subnet registration. Localnet UID slots do not represent production participant sets on live subnets.
On testnet, registration assigns UIDs on a shared non-production network. Testnet metagraph entries are separate from mainnet subnet state (Understanding Subnets).
On mainnet, a UID identifies a participant position on the selected netuid in live metagraph data (Glossary: Metagraph).
The Bittensor Networks reference separates mainnet, testnet, and localnet. A UID example from one environment should not be read as identifying a participant on another network.
Reader Boundary
UID is concept vocabulary for subnet participant identification. It should not be read as a network address, a balance container, or a cross-subnet identity (Glossary: UID slot).
UIDs can change through deregistration. A UID that identifies one participant today may identify a different participant in the same subnet after a registration event (Understanding Subnets).
Immunity Can Shield a New UID From Displacement
Mining: Miner deregistration documentation explains that when a subnet is full, a new registration can replace the lowest-emission eligible entrant. An entrant still inside the immunity period is protected from that ordinary removal path.
That timing rule attaches to the UID slot, not to the hotkey in isolation. A newly registered UID can keep its slot while immunity lasts even if performance is still developing.
Full Subnets Replace the Lowest Eligible UID
When every UID slot is occupied, the
subnet reaches its max_allowed_uids ceiling and new
registration attempts depend on
displacement rules rather than empty slots
(Subnet Hyperparameters).
UID vocabulary names which position changes hands. Displacement removes one eligible incumbent so a new registrant can take that numbered slot under subnet rules.
Weight Vectors Score Miners at Their UIDs
Yuma Consensus describes validators submitting vectors that rank miner work they have evaluated. Those scores attach to miners identified by UID inside the subnet participant set, not as a network-wide identity label (Glossary: Weight Vector).
Readers tracing consensus inputs should pair UID with netuid. The same numeric UID on different subnets refers to different participant positions.
Relationship to Hotkey
UID and hotkey are related but different registration terms. UID names the subnet-local slot number a participant occupies inside one subnet, while hotkey names the account key that signs operations and registers to that subnet (Glossary: UID slot, Glossary: Hotkey).
For readers, the UID is the position a registration produces and the hotkey is the key that requests it. Registration assigns a UID to a hotkey, so the hotkey is the account identity while the UID is the subnet slot that identity earns (Glossary: Register).
These terms sit on different layers. A hotkey is the same key identity across subnets, while the same numeric UID on different subnets refers to different participant positions, so one hotkey can hold different UIDs in different subnets (Understanding Subnets).
Readers should not treat a UID as proof of a specific hotkey across the network, or a hotkey mention as a substitute for the per-subnet UID it currently holds inside a chosen subnet.