getblockhash

getblockhash takes a block height and returns the hex hash of the block at that position on Bitcoin's active chain. Most Bitcoin block RPCs — getblock, getblockheader, getblockstats — are keyed by hash rather than height, so this method is the bridge that turns a human-friendly height (the genesis block is 0, and each later block adds another ~10 minutes of BTC settlement) into the hash those calls expect. Send the request to https://bitcoin.therpc.io/YOUR_API_KEY with the height as the single positional parameter.

Use cases

• Resolve a height to its hash so you can then call getblock or getblockheader.
• Walk the chain height by height inside an indexer, incrementing the counter as you go.
• Look up Bitcoin's genesis block by passing height 0.

Parameters

Response

Example request

1curl https://bitcoin.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5  "jsonrpc": "1.0",
6  "id": "therpc",
7  "method": "getblockhash",
8  "params": [
9    0
10  ]
11}'

Errors & troubleshooting

Common pitfalls

• Height 0 returns the genesis hash; a negative height or one above the current tip fails with error -8, "Block height out of range".
• After a reorg, the same height can map to a different hash, so re-resolve the height rather than caching the hash when reorg safety matters.

Supported networks

• Mainnet
• Testnet

See also

• getblock
• getblockheader
• getblockcount