Polkadot no longer runs parachain slot auctions. A blockchain now gets access by buying coretime with DOT, either in bulk for continuous use or on demand for occasional blocks. Coretime buys validation by the relay chain's validators, which is what shared security means: the connected chain inherits the relay chain's guarantees, and its reverts.
Polkadot no longer runs parachain slot auctions. A blockchain now gets access by buying coretime with DOT, either in bulk for continuous use or on demand for occasional blocks. Coretime buys validation by the relay chain's validators, which is what shared security means: the connected chain inherits the relay chain's guarantees, and its reverts.
Most explanations still in circulation describe the auction system. That system is deprecated, so a reader following older material is learning a mechanism that no longer operates. This guide covers what replaced it, and what a chain accepts in exchange for security it did not have to build.
What the relay chain does
Polkadot is arranged around one central chain, called the relay chain. Its job is deliberately small. The Polkadot Wiki describes its primary purpose as block production, core scheduling, data availability, and providing shared security to the rest of the network.
Three of those terms need unpacking.
A validator is a computer that checks proposed blocks, agrees with other validators on which are valid, and is penalised for misbehaviour. A core is a unit of the relay chain's validation capacity: a chain with a core assigned to it can have its blocks checked and recorded. Data availability means the relay chain guarantees that the data behind a block was actually published, so anyone can verify it later.
Functions a user would recognise have been moved off the relay chain. Staking and transfers now live on system parachains such as Asset Hub. The central chain does the scheduling and the security, and very little else.
What a parachain is
A parachain is a separate blockchain that connects to the relay chain. The Wiki defines it as an application-specific data structure that is globally coherent and can be validated by the validators of the relay chain.
In plainer terms: the chain keeps its own rules, its own accounts and its own blocks. What it does not keep is its own validator set. It hands each block to Polkadot's validators, who check it and record the result on the relay chain. That handover is the whole relationship, and everything below follows from it.
Did Polkadot end parachain auctions?
Yes. Auctions are deprecated in favour of coretime, and the two models work differently enough that the older description is misleading rather than merely dated.
Under the old model, a project competed for a lease on a parachain slot. DOT was locked for the duration and returned afterwards, often gathered from many holders through a crowdloan. Winning bought a long, fixed commitment; losing meant waiting for another auction.
Under coretime, access is a purchase of validation time rather than a contest for a seat.
| Property | Slot auctions, deprecated | Coretime, current |
|---|---|---|
| How a chain gets access | Wins a competitive auction for a slot lease | Buys time on a core with DOT |
| What happens to the DOT | Locked for the lease term, returned at the end | Spent on the purchase |
| Size of the commitment | One long fixed lease, arranged up front | A bulk period, or a single block on demand |
| Who could take part | Projects able to assemble a large lock, often through a crowdloan | Any project able to buy coretime |
| If a chain misses out | Wait for the next auction | Buy on-demand access per block instead |
The practical effect is that the entry step changed shape. A chain that only needs to produce a block occasionally no longer has to obtain the same commitment as a chain producing blocks constantly.
Bulk coretime and on-demand coretime
Both kinds of parachain buy time on a core with DOT. What differs is how that time is held.
A dedicated parachain runs constantly on its own core. It buys coretime in bulk, and holds capacity for the period instead of requesting it block by block.
An on-demand parachain shares cores with others. It buys the right to have a block validated when it has a block to produce. This suits a chain with intermittent activity, which would otherwise be paying to hold capacity it rarely uses.
What shared security actually commits a chain to
Shared security is usually described from one side only: a new chain gets the protection of a large validator set without recruiting one. That half is real. The Wiki puts it precisely, saying that the shared state ensures the trust assumptions when using parachains are only those of the relay chain validator set and no other.
The other half is the part worth stating plainly. Parachains share state with the relay chain, and the Wiki is direct about the consequence: if the relay chain must revert for any reason, then all of the parachains would also revert.
To revert is to discard blocks the network had already produced and return to an earlier state. On a chain with its own validators, a revert is that chain's own problem, caused by its own fault. A parachain has no such boundary. A relay chain revert takes every connected chain back with it, whatever those chains were doing at the time and whether or not they were involved.
This is the design trade-off in one line. A chain that runs its own validator set carries its own security budget and its own failure modes. A parachain carries Polkadot's, in both directions.
What DOT is used for
The token has three protocol roles.
- Staking. Nominators bond stake behind validators and share in the rewards, which is how the validator set is secured.
- Governance. DOT holders vote through Polkadot OpenGov, the network's on-chain decision-making system.
- Coretime. DOT is what buys time on a core, for bulk and on-demand access alike.
One historical detail causes confusion when reading older material. Polkadot launched in 2020, and DOT was redenominated in August of that year, with one old DOT becoming one hundred new DOT. That changed the unit of account only. Nobody's proportional holding changed, but any pre-redenomination quantity in an old document is out by a factor of one hundred.
Where to look next
- Polkadot price in AUD for the live figure, chart and source.
- Crypto prices in Australian dollars for the other coins Tradergy tracks.
- Glossary for plain definitions of the market terms used across the site.
- Guides for the rest of the explainer set.
Sources
- Architecture, Polkadot Wiki, as of September 2026: relay chain functions, the trust assumptions of shared security, and the shared-revert consequence.
- Parachains, Polkadot Wiki, as of September 2026: the definition of a parachain, and dedicated against on-demand coretime.
- Parachain Slot Auctions, Polkadot Wiki, as of September 2026: auctions ran until the Agile Coretime runtime upgrade of 19 September 2024, when ongoing auctions were cancelled and existing leases migrated.
- Agile Coretime, Polkadot Wiki, as of September 2026: bulk coretime as a fixed 28 day region, and on-demand coretime bought for the validation of a single parachain block.
- Polkadot, the project's own site.
General educational information about how the Polkadot protocol works. Not advice, not a recommendation to buy, hold or stake anything, and not a view on any price. Tradergy keeps no account and collects no personal data. Reviewed by the Tradergy editorial team, September 2026.
Common questions
What is Polkadot coretime?
Coretime is time on a core, meaning a share of the Polkadot relay chain's validation capacity. A blockchain buys coretime with DOT so that Polkadot's validators check and include its blocks. It replaced the older system in which chains competed at auction for a fixed lease on a parachain slot.
Did Polkadot end parachain auctions?
Yes. Parachain slot auctions are deprecated. Access to Polkadot is now obtained by buying coretime, in bulk for a chain that needs a core continuously or on demand for a chain that only needs blocks occasionally. Documentation that still describes candle auctions and crowdloans is describing a retired mechanism.
What is the difference between bulk coretime and on-demand coretime?
Bulk coretime gives a chain a core for a period, so it can produce blocks continuously on capacity it holds. On-demand coretime is bought block by block from shared capacity, which suits a chain that does not need to produce a block at every opportunity.
How does Polkadot shared security work?
Connected chains do not recruit their own validator sets. They hand their blocks to the relay chain's validators, so the trust assumptions of using a parachain are the trust assumptions of the relay chain validator set and nothing else. The same arrangement means a relay chain revert reverts every parachain with it.
What is a parachain in simple terms?
A parachain is a separate blockchain that plugs into Polkadot. It keeps its own rules, its own state and its own blocks, and hands each block to Polkadot's validators for checking rather than running a validator set of its own.