Getbestblockhash

getbestblockhash

Returns the hash of the best (tip) block in the most-work fully-validated chain.

Result:
"hex"      (string) the block hash, hex-encoded

Examples:
> bitcoin-cli getbestblockhash 
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "getbestblockhash", "params": [] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/