Returns an object containing various state info regarding block chain processing.

"chain": "xxxx", (string) current network name as defined in BIP70 (main, test, regtest)
"blocks": xxxxxx, (numeric) the current number of blocks processed in the server
"headers": xxxxxx, (numeric) the current number of headers we have validated
"bestblockhash": "...", (string) the hash of the currently best block
"difficulty": xxxxxx, (numeric) the current difficulty
"mediantime": xxxxxx, (numeric) median time for the current best block
"verificationprogress": xxxx, (numeric) estimate of verification progress [0..1]
"chainwork": "xxxx" (string) total amount of work in active chain, in hexadecimal
"pruned": xx, (boolean) if the blocks are subject to pruning
"pruneheight": xxxxxx, (numeric) lowest-height complete block stored
"softforks": [ (array) status of softforks in progress
"id": "xxxx", (string) name of softfork
"version": xx, (numeric) block version
"enforce": { (object) progress toward enforcing the softfork rules for new-version blocks
"status": xx, (boolean) true if threshold reached
"found": xx, (numeric) number of blocks with the new version found
"required": xx, (numeric) number of blocks required to trigger
"window": xx, (numeric) maximum size of examined window of recent blocks
"reject": { ... } (object) progress toward rejecting pre-softfork blocks (same fields as "enforce")
}, ...
"bip9_softforks": { (object) status of BIP9 softforks in progress
"xxxx" : { (string) name of the softfork
"status": "xxxx", (string) one of "defined", "started", "locked_in", "active", "failed"
"bit": xx, (numeric) the bit (0-28) in the block version field used to signal this softfork (only for "started" status)
"startTime": xx, (numeric) the minimum median time past of a block at which the bit gains its meaning
"timeout": xx (numeric) the median time past of a block at which the deployment is considered failed if not yet locked in

> bitcoin-cli getblockchaininfo
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "getblockchaininfo", "params": [] }' -H 'content-type: text/plain;'
Don't trust. Verify. Docs extracted from src/rpc/blockchain.cpp#L879-L922.