The JSON format - Bloklake

POST /query/json takes the same body as /query and returns one JSON object: one array per row type you asked for, plus the response metadata.

{
  "archive_height": 19427499,
  "finalized_block": 19427499,
  "from_block": 19426000,
  "to_block": 19426000,
  "next_block": 19426001,
  "objects": 605,
  "query_id_template": "0x22df2a6e1f32612c0db47f8e1e893ba9592a529613d0ced777513bb3d1d0dc4a",
  "to_block_hash": null,
  "unavailable_fields": ["blocks.total_difficulty"],
  "transactions": [
    {
      "hash": "0xa3958506c9bae6c6a3d5c7861b9461d01ddb33eca01b461920d59c31ed710275",
      "from": "0xae2fc483527b8ef99eb5d9b44875f005ba1fae13",
      "to": "0x6b75d8af000000e20b7a7ddf000ba900b4009a80",
      "value": "208",
      "gas_used": 435741,
      "effective_gas_price": "51321417043",
      "status": 1,
      "type": 2,
      "sighash": "0x2b959e09"
    }
  ],
  "logs": [
    {
      "address": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2",
      "block_number": 19426000,
      "log_index": 0,
      "topic0": "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
      "topic1": "0x0000000000000000000000009e0905249ceefffb9605e034b534544684a58be6",
      "topic2": "0x0000000000000000000000006b75d8af000000e20b7a7ddf000ba900b4009a80",
      "topic3": null,
      "data": "0x000000000000000000000000000000000000000000000000081bbb9200000001"
    }
  ],
  "blocks": [
    {
      "number": 19426000,
      "hash": "0xccabd8d387536006b0d08eae80c10cfce6eaeefefa43f5f02d35727ff84e19f8",
      "timestamp": 1710331067,
      "base_fee_per_gas": "51321417043",
      "total_difficulty": null,
      "withdrawals": [
        {"index": 38256630, "validator_index": 1258775, "address": "0xb9d7934878b5fb9610b3fe8a5e441e8fad7e293f", "amount": 18045827}
      ]
    }
  ]
}

(A real response, shortened to one row per row type.)

How values are written

Kind of field	Arrow type	JSON	Example
Block numbers, indexes, gas, nonces, timestamps	`UInt64` / `UInt32` / `UInt8`	number	`19426000`
Amounts: `value`, gas prices, fees, `difficulty`	`FixedSizeBinary(16)`	decimal string	`"51321417043"`
256-bit amounts (Arbitrum retryables)	`FixedSizeBinary(32)`	decimal string	`"115792089…"`
Hashes, topics, roots	`FixedSizeBinary(32)`	`0x` hex, lowercase	`"0xccab…19f8"`
Addresses	`FixedSizeBinary(20)`	`0x` hex, lowercase	`"0xc02a…6cc2"`
Variable bytes: `input`, `data`, `extraData`	`Binary`	`0x` hex (`"0x"` when empty)	`"0x2b959e09…"`
Block `nonce`, `sighash`, `logsBloom`	`FixedSizeBinary(8/4/256)`	`0x` hex	`"0x0000000000000000"`
Lists	`List<…>`	array	`["0x…", "0x…"]`
Structs (`withdrawals`, `accessList` entries)	`Struct`	object with snake_case keys	`{"index": 1, …}`
Booleans (`status`, `timeboosted`, `isSystemTx`)	`UInt8`	`1` / `0`	`1`
Missing	null	`null`	`null`

Amounts are strings because they can exceed what a JSON number (a 64-bit float) holds exactly: value is in wei and routinely above 2⁵³. Parse them as big integers (BigInt(s), Python int(s)). The integer fields that are JSON numbers stay below 2⁵³ in practice.

Limits

Up to 100,000 rows per response. maxObjects is lowered to that, and next_block resumes after the last block returned. Like Arrow pages, a page can overshoot by one block.
Built in full before it’s sent. Nothing arrives until the whole response is ready, and it takes more memory on both sides. Prefer /query for anything large.
Billed on the JSON size, which is about 2–2.5× the Arrow size of the same rows. See Arrow vs JSON.

Errors

An error is a non-200 status with a JSON body:

{"error": {"code": "invalid_query", "message": "unknown field \"adress\" in fields.log"}}

See Errors.