A transaction hash is a lookup key
Given just a hash and the chain it was sent on, a full node can return everything about that transaction — who sent it, where it went, what it moved, whether it succeeded, and exactly what it cost in gas. This tool makes that same lookup that every block explorer performs, directly from your browser.
How it works
Two RPC calls: eth_getTransactionByHash for the transaction itself, and eth_getTransactionReceipt for its outcome (success/reverted, gas used, effective gas price) — the receipt only exists once the transaction is actually mined.