Block number

A block number (often called block height) is the sequential index of

a block on a blockchain. The genesis block is block 0 (or 1, depending on

the chain's convention), and each subsequent block on the canonical chain

gets the next integer. Paste a block number at tx.taxi/{number} and you

are routed to the configured explorer's block page.

Why block numbers are cleaner identifiers

Compared to a block hash, a block number is short,

human-readable, and monotonically increasing. That is why explorer URLs

typically link blocks by number:

• etherscan.io/block/19000000 for an ethereum block.
• bscscan.com/block/40000000 for a bsc block.
• mempool.space/block/800000 for a bitcoin block.

URLs built on numbers stay readable in references, documentation, and chat

messages. They also make ranges easy to express ("blocks 19000000 to

19000100"), which is the natural unit for indexers and analytics tools.

The catch: numbers are not unique across forks

A block number alone does not name a unique block. When a chain briefly

forks, two competing blocks can share the same height while having

different block hashes. Only one of them ends up on the canonical chain.

This matters most on chains with probabilistic finality, such as

bitcoin, where shallow blocks at the tip may still be

reorganised away. After enough

confirmations, the block at a given height

is effectively settled.

Chains with deterministic finality (such as

solana once a slot is finalised, aptos,

and sui) collapse this ambiguity faster, but the principle

still holds: the canonical block at a height is defined by the protocol's

finality rules, not by the height alone.

How explorers and tools use it

Block numbers appear everywhere in tooling:

• Explorer URLs use /block/{number} as the primary form, with the block

hash as an alternative path.

• RPC methods such as eth_getBlockByNumber accept the integer directly,

along with special tags like latest, earliest, safe, and

finalized on EVM chains.

• Event indexers query logs in block ranges, which is why historical

queries are often phrased as "from block X to block Y".

• A transaction hash is associated with a

specific block number once it is included, and the receipt records that

number.

Common gotchas

• Block numbers across different chains do not correspond to the same

point in time. Ethereum, Solana, and Bitcoin all produce blocks at very

different rates. A "block 19000000" reference is meaningless without

naming the chain.

• Some chains have non-contiguous slot numbers. Solana uses slots, and

not every slot produces a finalized block; you may see gaps when paging

through history.

• A block number you see in a wallet UI is informational. The

authoritative reference for a confirmed transaction is the

block hash plus the transaction index within it.