Extrinsics, events, and why the vocabulary matters
Substrate chains do not have transactions in the sense other chains use the word. They have extrinsics — pieces of information from outside the chain that trigger state changes — and events, which are what those state changes emit.
This is not pedantry. An extrinsic can be signed by an account or unsigned, it can be submitted by the chain itself as an inherent, and one extrinsic can produce many events. A generic explorer looking for "transactions" finds a subset and misses the rest.
Subscan is built around the correct model. Every extrinsic page lists the module and call that was invoked, the parameters, and every event it produced. If you are trying to understand what actually happened on a Substrate chain, that structure is the only one that works.
The cost is a learning curve. You will meet balances.transferKeepAlive, staking.nominate and utility.batchAll before anything translates the terms for you. Subscan assumes you either know or will look it up.
Staking, which is the reason most people arrive
Polkadot's nominated proof-of-stake is more elaborate than the staking most people have encountered, and Subscan is where it becomes comprehensible.
Rewards are calculated per era — roughly a day on Polkadot, six hours on Kusama — and distributed to validators, who pass a share to their nominators after taking commission. Your return therefore depends on which validators you nominated, whether they were active in that era, their commission, and whether they were slashed.
Subscan shows all of it: era-by-era reward history, the validators you actually backed in each era rather than the ones you nominated, commission changes over time, and any slashing events. The distinction between nominated and active validators is the one that catches people — you can nominate sixteen and be backing only one in a given era, and if that one is inactive you earn nothing.
It also tracks unbonding. Polkadot's unbonding period is twenty-eight days, and funds sit unavailable throughout. Subscan shows where each tranche is in that countdown, which is otherwise close to impossible to establish.
Governance: constitutional process, on chain
Polkadot runs one of the more ambitious on-chain governance systems in existence. Referenda are proposed, voted on with conviction weighting — lock your tokens longer, count for more — and executed automatically by the chain if they pass. Treasury spending goes through the same machinery.
Subscan surfaces the whole process: active referenda with their tracks and thresholds, vote tallies split by conviction, the actual call a referendum would execute if enacted, and treasury proposals with their beneficiaries and amounts.
That last point deserves emphasis. Because governance actions are on-chain calls, you can read exactly what a referendum will do rather than relying on its description. A proposal titled one thing and encoding another is detectable, and Subscan is where you would detect it. That is a genuine accountability mechanism and very few chains have anything equivalent.
XCM, and why nothing else tracks it
Polkadot's architecture is a relay chain with parachains connected to it, and XCM — Cross-Consensus Messaging — is how they communicate. Moving an asset from one parachain to another is an XCM message, not a transaction on either chain in the usual sense.
This produces the familiar cross-chain confusion in an unfamiliar form. You initiate a transfer on parachain A, it disappears, and it appears on parachain B some time later with a different identifier. Search for the original hash on the destination and you find nothing.
Subscan tracks XCM messages across chains and links both ends. As far as we can establish it is the only explorer that does this, which makes it not merely the best option for Polkadot transfers but the only one.
The pattern, again
This is the third time it appears in our reviews: Arbitrum L1/L2 messages, TON message chains, Polkadot XCM. Any time a system is asynchronous or spans chains, one action becomes several records and the identifier does not carry across. If a transfer has "vanished", the first hypothesis should always be that you are searching for the right thing in the wrong place.
API and open source
Subscan publishes its code and offers a free API tier with a key, with paid plans for production volume. The free allowance is workable for scripts and dashboards, tight for anything user-facing.
Being open source matters here more than usual. Substrate chains are configurable — each one enables different pallets, which means different extrinsics, events and data shapes. An explorer handling a hundred chains is making per-chain decisions constantly, and being able to read those decisions is the difference between trusting the output and verifying it.
For EVM-compatible parachains such as Moonbeam, you will want both Subscan and an EVM explorer. Moonscan shows the EVM side; Subscan shows the Substrate side. The same chain, two incompatible views, both incomplete alone.