Removed Protocol Methods

This documents protocol methods that are still supported in some protocol versions, but not the most recent one.

Deserialized Headers

A deserialized header is a dictionary describing a block at a given height.

A typical example would be similar to this template:

  "block_height": <integer>,
  "version": <integer>,
  "prev_block_hash": <hexadecimal string>,
  "merkle_root":  <hexadecimal string>,
  "timestamp": <integer>,
  "bits": <integer>,
  "nonce": <integer>


The precise format of a deserialized block header varies by coin, and also potentially by height for the same coin. Detailed knowledge of the meaning of a block header is neither necessary nor appropriate in the server. Consequently they were removed from the protocol in version 1.4.


Subscribe to receive block headers when a new block is found.


Changed in version 1.2: Optional raw parameter added, defaulting to false.

Changed in version 1.3: raw parameter deafults to true.

Changed in version 1.4: raw parameter removed; responses and notifications pass raw headers.

  • raw

    This single boolean argument exists in protocol versions 1.2 (defaulting to false) and 1.3 (defaulting to true) only.


The header of the current block chain tip. If raw is true the result is a dictionary with two members:

  • hex

    The binary header as a hexadecimal string.

  • height

    The height of the header, an integer.

If raw is false the result is the coin-specific deserialized header.

Example Result

With raw false:

  "bits": 402858285,
  "block_height": 520481,
  "merkle_root": "8e8e932eb858fd53cf09943d7efc9a8f674dc1363010ee64907a292d2fb0c25d",
  "nonce": 3288656012,
  "prev_block_hash": "000000000000000000b512b5d9fc7c5746587268547c04aa92383aaea0080289",
  "timestamp": 1520495819,
  "version": 536870912

With raw true:

  "height": 520481,
  "hex": "00000020890208a0ae3a3892aa047c5468725846577cfcd9b512b50000000000000000005dc2b02f2d297a9064ee103036c14d678f9afc7e3d9409cf53fd58b82e938e8ecbeca05a2d2103188ce804c4"


As this is a subcription, the client will receive a notification when a new block is found. The notification’s signature is:

  • header

    See Result above.


should a new block arrive quickly, perhaps while the server is still processing prior blocks, the server may only notify of the most recent chain tip. The protocol does not guarantee notification of all intermediate block headers.

In a similar way the client must be prepared to handle chain reorganisations. Should a re-org happen the new chain tip will not sit directly on top of the prior chain tip. The client must be able to figure out the common ancestor block and request any missing block headers to acquire a consistent view of the chain state.


Subscribe to receive the block height when a new block is found.



Deprecated since version 1.0: removed in version 1.1


The height of the current block, an integer.


As this is a subcription, the client will receive a notification when a new block is found. The notification’s signature is:



Return the address paid to by a UTXO.


blockchain.utxo.get_address(tx_hash, index)

Optional in version 1.0, removed in version 1.1


The transaction hash as a hexadecimal string.


The zero-based index of the UTXO in the transaction.


A Base58 address string, or null. If the transaction doesn’t exist, the index is out of range, or the output is not paid to an address, null must be returned. If the output is spent null may be returned.


Return the deserialized header of the block at the given height.



Deprecated since version 1.3: removed in version 1.4


The height of the block, an integer.


The coin-specific deserialized header.

Example Result

  "bits": 392292856,
  "block_height": 510000,
  "merkle_root": "297cfcc6a66e063692b20650d21cc0ac7a2a80f7277ebd7c5d6c7010a070d25c",
  "nonce": 3347656422,
  "prev_block_hash": "0000000000000000002292de0d9f03dfa15a04dbf09102d5d4552117b717fa86",
  "timestamp": 1519083654,
  "version": 536870912


Return a concatenated chunk of block headers from the main chain. Typically, a chunk consists of a fixed number of block headers over which difficulty is constant, and at the end of which difficulty is retargeted.

In the case of Bitcoin a chunk is 2,016 headers, each of 80 bytes, so chunk 5 consists of the block headers from height 10,080 to 12,095 inclusive. When encoded as hexadecimal, the result string is twice as long, so for Bitcoin it takes 322,560 bytes, making this a bandwidth-intensive request.



Deprecated since version 1.2: removed in version 1.4


The zero-based index of the chunk, an integer.


The binary block headers as hexadecimal strings, in-order and concatenated together. As many as headers as are available at the implied starting height will be returned; this may range from zero to the coin-specific chunk size.


Identify the client to the server and negotiate the protocol version.


Changed in version 1.1: protocol_version is not ignored.

Changed in version 1.2: Use rather than sending version requests as a ping mechanism.

Changed in version 1.4: Only the first server.version() message is accepted.

  • client_name

    A string identifying the connecting client software.

  • protocol_version

    An array [protocol_min, protocol_max], each of which is a string. If protocol_min and protocol_max are the same, they can be passed as a single string rather than as an array of two strings, as for the default value.

The server should use the highest protocol version both support:

version = min(client.protocol_max, server.protocol_max)

If this is below the value:

max(client.protocol_min, server.protocol_min)

then there is no protocol version in common and the server must close the connection. Otherwise it should send a response appropriate for that protocol version.


An array of 2 strings:

[server_software_version, protocol_version]

identifying the server and the protocol version that will be used for future communication.

Protocol version 1.0: A string identifying the server software.


server.version("Electrum 3.0.6", ["1.1", "1.2"])
server.version("2.7.1", "1.0")

Example Results:

["ElectrumX 1.2.1", "1.2"]
"ElectrumX 1.2.1"