Nervos CKB

Nervos CKB API is available on Web3 API platform (opens in a new tab).

Nervos CKB (Common Knowledge Base) is the Layer 1, proof-of-work blockchain of the Nervos ecosystem. As the foundation of the ecosystem, it provides trust for all the layers built on top of it. CKB uses an improved Nakamoto consensus (NC-Max) and a generalized UTXO model — the Cell model — designed to maximize decentralization while remaining minimal, flexible, and secure. Its primary objective is to reliably preserve any data and assets stored therein.

The Nervos EVM / Polyjuice (Godwoken) Layer 2 endpoint (rpc.ankr.com/nervos) has been deprecated and removed. Nervos officially sunset the Godwoken network starting June 2025 (a strategic shift toward UTXO-native protocols such as RGB++), so the network is no longer operational upstream. See the official Godwoken & Force Bridge sunset announcement (opens in a new tab). Only the native Nervos CKB (Layer 1) endpoint documented below is available.

In order for your Web3 application to interact with Nervos CKB — either by reading blockchain data or sending transactions to the network — it must connect to a CKB node. Developers interact with the blockchain using the methods provided by the API.

The API interaction follows the JSON-RPC (opens in a new tab) which is a stateless, light-weight remote procedure call (RPC) protocol. It uses JSON (RFC 4627) as data format. CKB exposes its JSON-RPC over HTTPS and WSS.

Endpoint format:

https://rpc.ankr.com/nervos_ckb/{your_token}

Official quick links: Website (opens in a new tab), CKB Docs (opens in a new tab), JSON-RPC reference (opens in a new tab), GitHub (opens in a new tab)

Methods supported

get_tip_block_number — returns the highest block number in the canonical chain.
get_tip_header — returns the header with the highest block number in the canonical chain.
get_current_epoch — returns the epoch with the highest number in the canonical chain.
get_block_by_number — returns the block in the canonical chain with the specified block number.
get_block — returns the information about a block by hash.
get_header — returns the information about a block header by hash.
get_header_by_number — returns the block header in the canonical chain with the specified block number.
get_block_hash — returns the block hash of a block in the canonical chain by block number.
get_transaction — returns the information about a transaction by hash, including its status.
get_live_cell — returns the status of a cell, optionally with its data.
get_consensus — returns various consensus parameters.
get_fee_rate_statistics — returns the fee rate statistics of confirmed blocks.
get_blockchain_info — returns general information about the chain.
tx_pool_info — returns the transaction pool information.
send_transaction — submits a new transaction into the transaction pool.
test_tx_pool_accept — tests whether the transaction pool would accept a transaction.

CKB encodes integers as 0x-prefixed hexadecimal strings (e.g. block number 0x12a6ad1). Block hashes and other byte fields are 0x-prefixed hex.

Node administration, mining and network-control methods are not exposed on the shared endpoint — e.g. local_node_info, get_peers, get_banned_addresses, set_ban, sync_state, add_node, remove_node, clear_tx_pool, truncate, generate_block, miner methods (get_block_template, submit_block) and debug_*. For dedicated access, contact Sales (sales@ankr.com) about the Enterprise plan.

`get_tip_block_number`

Returns the highest block number in the canonical chain.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required): None.

Returns

<string> (BlockNumber): the highest block number in the canonical chain, as a 0x-prefixed hex string.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_tip_block_number",
      "params": [],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "result": "0x12a69e1",
    "id": 1
}

`get_tip_header`

Returns the header with the highest block number in the canonical chain.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array): optionally a verbosity <string> (0x0 returns the serialized header; 0x1, the default, returns a JSON header object).

Returns

<object> (HeaderView): the block header, including number, hash, parent_hash, timestamp, epoch, compact_target, dao, nonce, transactions_root, extra_hash, proposals_hash and version.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_tip_header",
      "params": [],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "compact_target": "0x1913ca98",
        "dao": "0x0be3ccb2b7279c59cd86a389ab882a00fe62c81b1474e9090068f4dfb7183707",
        "epoch": "0x524029e003810",
        "extra_hash": "0x6ce92f725a28bae121cf062051a95f6b843bc52c9ed75cd17d600f8efdeffd3f",
        "hash": "0xaa8d68b396f8a01449d829fef85c4065c83e6fa71ec7b1f066674ff752dd0d01",
        "nonce": "0x4826eb8b5c783719000000092f10020e",
        "number": "0x12a6ad1",
        "parent_hash": "0x395a24dc75784a8e0a08f712c1186b8e74bf3d6e6fe5c2a0592cdf443725dde6",
        "proposals_hash": "0x0000000000000000000000000000000000000000000000000000000000000000",
        "timestamp": "0x19eb091b1a5",
        "transactions_root": "0x4343d4eec2b8d1d082fafc8cc056b250bb6ca853d99c5acdbc54555cbbcc7677",
        "version": "0x0"
    }
}

`get_current_epoch`

Returns the epoch with the highest number in the canonical chain.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required): None.

Returns

<object> (EpochView):
- number (string): the epoch number.
- start_number (string): the block number of the first block in the epoch.
- length (string): the number of blocks in the epoch.
- compact_target (string): the difficulty target of the epoch, in compact form.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_current_epoch",
      "params": [],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "compact_target": "0x1913ca98",
        "length": "0x524",
        "number": "0x3810",
        "start_number": "0x12a6833"
    }
}

`get_block_by_number`

Returns the block in the canonical chain with the specified block number.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <string> (BlockNumber): the block number, as a 0x-prefixed hex string.
2. <string> (optional): verbosity — 0x0 returns the serialized block; 0x2 (the default) returns a JSON block object.
3. <boolean> (optional): with_cycles — if true, the response also includes the execution cycles of each transaction.

Returns

<object> (BlockView): the block, containing a header, the transactions array, the proposals array and uncles. Returns null when there is no block at the given number.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_block_by_number",
      "params": ["0x12a6ad1"],
      "id": 1
    }'

Response example (trimmed)

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "header": {
            "compact_target": "0x1913ca98",
            "epoch": "0x524029e003810",
            "hash": "0xaa8d68b396f8a01449d829fef85c4065c83e6fa71ec7b1f066674ff752dd0d01",
            "number": "0x12a6ad1",
            "parent_hash": "0x395a24dc75784a8e0a08f712c1186b8e74bf3d6e6fe5c2a0592cdf443725dde6",
            "timestamp": "0x19eb091b1a5",
            "transactions_root": "0x4343d4eec2b8d1d082fafc8cc056b250bb6ca853d99c5acdbc54555cbbcc7677",
            "version": "0x0"
        },
        "proposals": [],
        "transactions": [
            {
                "cell_deps": [],
                "header_deps": [],
                "hash": "0x...",
                "inputs": [],
                "outputs": [],
                "outputs_data": [],
                "version": "0x0",
                "witnesses": []
            }
        ],
        "uncles": []
    }
}

`get_block`

Returns the information about a block by hash.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <string> (H256): the block hash (32 bytes, 0x-prefixed).
2. <string> (optional): verbosity — 0x0 or 0x2 (default).
3. <boolean> (optional): with_cycles.

Returns

<object> (BlockView): the block (same structure as get_block_by_number). Returns null when the block is not found.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_block",
      "params": ["0xaa8d68b396f8a01449d829fef85c4065c83e6fa71ec7b1f066674ff752dd0d01"],
      "id": 1
    }'

Response example

A BlockView object, identical in shape to the get_block_by_number response.

`get_header`

Returns the information about a block header by hash.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <string> (H256): the block hash.
2. <string> (optional): verbosity — 0x0 or 0x1 (default).

Returns

<object> (HeaderView): the block header (same structure as get_tip_header). Returns null when the header is not found.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_header",
      "params": ["0xaa8d68b396f8a01449d829fef85c4065c83e6fa71ec7b1f066674ff752dd0d01"],
      "id": 1
    }'

Response example

A HeaderView object, identical in shape to the get_tip_header response.

`get_header_by_number`

Returns the block header in the canonical chain with the specified block number.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <string> (BlockNumber): the block number.
2. <string> (optional): verbosity — 0x0 or 0x1 (default).

Returns

<object> (HeaderView): the block header. Returns null when there is no block at the given number.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_header_by_number",
      "params": ["0x12a6ad1"],
      "id": 1
    }'

Response example

A HeaderView object, identical in shape to the get_tip_header response.

`get_block_hash`

Returns the block hash of a block in the canonical chain by block number.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <string> (BlockNumber): the block number.

Returns

<string> (H256): the block hash, or null when there is no block at the given number.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_block_hash",
      "params": ["0x12a6ad1"],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": "0xaa8d68b396f8a01449d829fef85c4065c83e6fa71ec7b1f066674ff752dd0d01"
}

`get_transaction`

Returns the information about a transaction by hash, including its status.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <string> (H256): the transaction hash.
2. <string> (optional): verbosity — 0x0, 0x1 or 0x2 (default).
3. <boolean> (optional): only_committed — if true, only returns the transaction if it has been committed on chain.

Returns

<object> (TransactionWithStatus):
- transaction (object): the transaction (or null depending on verbosity / status).
- cycles (string): the consumed cycles, when available.
- tx_status (object): { status, block_hash, block_number, reason }. status is one of pending, proposed, committed, unknown or rejected.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_transaction",
      "params": ["0xa0 ... transaction hash ... 5b"],
      "id": 1
    }'

Response example (trimmed)

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "cycles": "0x219c",
        "transaction": { "hash": "0x...", "inputs": [], "outputs": [] },
        "tx_status": {
            "block_hash": "0xaa8d68b396f8a01449d829fef85c4065c83e6fa71ec7b1f066674ff752dd0d01",
            "block_number": "0x12a6ad1",
            "reason": null,
            "status": "committed"
        }
    }
}

`get_live_cell`

Returns the status of a cell. The RPC returns extra information if it is a live cell.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <object> (OutPoint): { "tx_hash": "<H256>", "index": "<hex>" } — the cell out point.
2. <boolean>: with_data — if true, the response includes the cell data.

Returns

<object> (CellWithStatus):
- cell (object): the cell output and optional data, when the cell is live.
- status (string): one of live, dead or unknown.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_live_cell",
      "params": [{ "index": "0x0", "tx_hash": "0xa0ef4eb5f4ce087db3ce8b58c1bb6c6f93a6c4d1c1f1f8f6f8b... " }, true],
      "id": 1
    }'

Response example (trimmed)

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "cell": {
            "data": { "content": "0x", "hash": "0x..." },
            "output": {
                "capacity": "0x802665800",
                "lock": { "args": "0x", "code_hash": "0x...", "hash_type": "type" },
                "type": null
            }
        },
        "status": "live"
    }
}

`get_consensus`

Returns various consensus parameters of the chain.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required): None.

Returns

<object> (Consensus): consensus parameters, including id, genesis_hash, primary_epoch_reward_halving_interval, epoch_duration_target, block_version, tx_version, max_block_cycles, max_block_bytes, dao_type_hash, secp256k1_blake160_sighash_all_type_hash, hardfork_features and more.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_consensus",
      "params": [],
      "id": 1
    }'

Response example (trimmed)

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "id": "ckb",
        "genesis_hash": "0x92b197aa1fba0f63633922c61c92375c9c074a93e85963554f5499fe1450d0e5",
        "epoch_duration_target": "0x3840",
        "max_block_bytes": "0x91c08",
        "max_block_cycles": "0xd09dc300",
        "block_version": "0x0",
        "tx_version": "0x0",
        "dao_type_hash": "0x82d76d1b75fe2fd9a27dfbaa65a039221a380d76c926f378d3f81cf3e7e13f2e"
    }
}

`get_fee_rate_statistics`

Returns the fee rate statistics of confirmed blocks on the chain.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array): optionally a <string> (hex) target — the number of confirmed blocks to look back over (default 0x15).

Returns

<object>: { "mean": "<hex>", "median": "<hex>" } — the mean and median fee rate (Shannons per kilo-weight) over the target window, or null when no statistics are available.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_fee_rate_statistics",
      "params": [],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "mean": "0x3e8",
        "median": "0x3e8"
    }
}

`get_blockchain_info`

Returns general information about the chain.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required): None.

Returns

<object> (ChainInfo):
- chain (string): the network name (e.g. ckb for mainnet).
- difficulty (string): the current difficulty.
- epoch (string): the current epoch number (packed).
- median_time (string): the median time of the last 37 blocks (milliseconds).
- is_initial_block_download (boolean): whether the node is still in initial block download.
- alerts (array): the active network alerts.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "get_blockchain_info",
      "params": [],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "alerts": [],
        "chain": "ckb",
        "difficulty": "0xcef571d05179903",
        "epoch": "0x524029e003810",
        "is_initial_block_download": false,
        "median_time": "0x19eb08ed9db"
    }
}

`tx_pool_info`

Returns the transaction pool information.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required): None.

Returns

<object> (TxPoolInfo):
- pending (string), proposed (string), orphan (string): the number of transactions in each state.
- total_tx_size (string), total_tx_cycles (string): the aggregate size and cycles of pool transactions.
- min_fee_rate (string), min_rbf_rate (string): the minimum fee rate for acceptance / replace-by-fee.
- tip_hash (string), tip_number (string): the chain tip the pool is based on.
- tx_size_limit (string), max_tx_pool_size (string), verify_queue_size (string), last_txs_updated_at (string).

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "tx_pool_info",
      "params": [],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "last_txs_updated_at": "0x19eb091d08b",
        "max_tx_pool_size": "0xaba9500",
        "min_fee_rate": "0x3e8",
        "min_rbf_rate": "0x5dc",
        "orphan": "0x0",
        "pending": "0x4",
        "proposed": "0x0",
        "tip_hash": "0xaa8d68b396f8a01449d829fef85c4065c83e6fa71ec7b1f066674ff752dd0d01",
        "tip_number": "0x12a6ad1",
        "total_tx_cycles": "0x67aa33",
        "total_tx_size": "0xc99",
        "tx_size_limit": "0x7d000",
        "verify_queue_size": "0x0"
    }
}

`send_transaction`

Submits a new transaction into the transaction pool.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <object> (Transaction): the transaction object (version, cell_deps, header_deps, inputs, outputs, outputs_data, witnesses).
2. <string> (optional): outputs_validator — passthrough or well_known_scripts_only (the default).

Returns

<string> (H256): the transaction hash.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "send_transaction",
      "params": [
        {
          "version": "0x0",
          "cell_deps": [],
          "header_deps": [],
          "inputs": [],
          "outputs": [],
          "outputs_data": [],
          "witnesses": []
        },
        "passthrough"
      ],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": "0xa0ef4eb5f4ce087db3ce8b58c1bb6c6f93a6c4d1c1f1f8f6f8b94c8f9b5e2c5b"
}

`test_tx_pool_accept`

Tests whether the transaction pool would accept a transaction, without actually submitting it.

Parameters

id (integer; required): a request ID (example: 1).
jsonrpc (string; required): a JSON RPC spec used (example: 2.0).
method (string; required): a method used for the request.
params (array; required):
1. <object> (Transaction): the transaction object (same structure as send_transaction).
2. <string> (optional): outputs_validator — passthrough or well_known_scripts_only (the default).

Returns

<object> (EntryCompleted): { "cycles": "<hex>", "fee": "<hex>" } — the consumed cycles and the fee the transaction would pay.

Request example

curl -X POST https://rpc.ankr.com/nervos_ckb/{your_token} \
-H 'Content-Type: application/json' \
-d '{
      "jsonrpc": "2.0",
      "method": "test_tx_pool_accept",
      "params": [
        {
          "version": "0x0",
          "cell_deps": [],
          "header_deps": [],
          "inputs": [],
          "outputs": [],
          "outputs_data": [],
          "witnesses": []
        },
        "passthrough"
      ],
      "id": 1
    }'

Response example

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": {
        "cycles": "0x219c",
        "fee": "0x16e"
    }
}

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