Why the number of headers and blocks are different?

Question

When I run $bitcoin-cli getblockchaininfo it shows me:

{
  "chain": "main",
  "blocks": 20204,
  "headers": 563653,
  ....
}

But if a block is identified by his header, the numbers of headers and block must be the same, what I didn't understand?

Answer 1

Please see Bitcoin RPC Documentation - getblockchaininfo

"blocks": xxxxxx,             (numeric) the current number of blocks processed in the server
"headers": xxxxxx,            (numeric) the current number of headers we have validated

blocks is the height of the highest downloaded and validated block, and headers is the height of the highest validated block header (minus one on both, since counting starts from zero). Validating a header by itself doesn't require the entire block.