What Arc is
Arc is a layer-1 blockchain built by Circle — a chain with its own validator set, its own consensus and its own finality. It is not a rollup, an optimistic chain or a validium: no batch of Arc transactions is posted to another blockchain for settlement, and no fraud-proof or validity-proof window exists, because nothing on Arc is waiting for another chain's confirmation.
That distinction has practical consequences for anyone reading this site:
- There is no “settled on L1” state to wait for, and no second explorer to check.
- There is no sequencer, and therefore no forced-inclusion escape hatch.
- A transaction's cost is determined entirely by Arc's own fee market, not by data-availability pricing somewhere else.
Two halves
Like most modern chains, Arc separates consensus from execution and joins them over the Engine API.
Consensus is Malachite, a Rust implementation of Tendermint-style BFT. A designated proposer builds a block, the validator set votes on it in prevote and precommit rounds, and once more than two thirds of the voting power has precommitted the block is committed — permanently. This is what gives Arc deterministic finality, covered in its own article.
Execution is Reth, the same Ethereum execution client used on Ethereum mainnet. That is why Arc speaks ordinary Ethereum JSON-RPC, why addresses are 20-byte EVM addresses, why contracts are EVM bytecode, and why almost every Ethereum tool works against it unchanged. Blocks carry the modern post-Prague header fields you would expect from Reth.
Two of those inherited fields are inert on Arc and this explorer treats them as such. uncles is always empty, because BFT consensus produces no orphaned blocks for there to be. parentBeaconBlockRoot is present because the header format requires it, but Arc has no beacon chain and the field simply repeats parentHash — measured identical on 40 out of 40 consecutive blocks — so Arcscan does not render it as though it meant something.
Shape of the chain
Blocks land roughly every 508 ms, which is about 62 million blocks a year, and a measured 60-block sample carried around 10 transactions per block with no empty blocks. The gas limit is 30,000,000 and blocks run a few per cent full, so congestion is not currently a thing that happens here. Block production rotates across the validator set — Arcscan labels the address that built a block Proposer, never “miner”, because there is no mining and no builder market.
Block timestamps are integer seconds while blocks arrive twice a second, so roughly two consecutive blocks share every timestamp. That is why nothing on this site sorts or pages by time — ordering is always by block height, which is exact.
The distinctive property, and the one everything else on this site bends around, is the gas token: fees on Arc are paid in USDC. That has consequences worth their own article too.