Storage writes of a transaction

Open this transaction in TraceFast →

Every contract storage slot a transaction wrote, in execution order: which contract's storage, which frame wrote it and whose code ran there, the slot, the value written, and the value the slot held before where that can be established. Contract storage is the persistent key-value store every contract keeps — balances, owners, configuration; see the EVM on ethereum.org.

GET https://tracefast.xyz/api/v1/chains/1/transactions/{hash}/storage-writes

Access — an API key on the Investigation plan or higher (plans), or no key at all: pay per call with x402 at the same path on https://mpp.tracefast.xyz/api/v1, at the price its 402 states. As a tool for AI agents: get_transaction_storage_writes on the MCP server. Stable — see stability.

chains/1 is a literal: the method serves Ethereum mainnet data. Other chain ids answer 404 chain_not_supported. There are no other parameters — an unknown one is refused rather than ignored.

What it covers, and what it does not

• The storage owner and the code are two addresses. On a delegatecall a proxy runs its implementation's code against its own storage: storageAddress is the contract whose storage changed, executionAddress the contract whose code wrote it.
• The value before is stated only when it can be. valueBefore is present only with valueBeforeStatus: resolved. not_computed means the prior value has not been computed for this write yet — it is not a statement that the slot was empty.
• Writes are computed up to a block. meta.coverage.storageWritesThroughBlock is the last block writes have reached. For a transaction in a later block the method answers 422 block_not_available with reason: coverage_gap — the writes are not available yet, which says nothing about what the transaction wrote. An empty writes list is never served for such a transaction.
• At most 5 000 slots. When a transaction wrote more, the last page says so with writesTruncated: true.

Response

200 application/json, here with ?limit=2 — a USDC transfer, which updates two balances through the proxy's delegatecall:

{
  "data": {
    "hash": "0xc41b41fb1c3eea59ea87b9e90edf476fb202e8daf02f19f469cdf497adbc76e0",
    "blockNumber": 25920000,
    "txIndex": 3,
    "writes": [
      {
        "writeIndex": 0,
        "writeIndexStatus": "present",
        "storageAddress": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
        "executionAddress": "0x43506849d7c04f9138d1a2050bbf3a0c054402dd",
        "callerAddress": "0x978e75381d64fb18af7112e42fa76a211a773456",
        "storageKey": "0xb4999ac4e72c403d0684d9ce54cbcb1cf6ff12691c1b573caa0f80fe2a7d4d55",
        "newValue": "0x00000000000000000000000000000000000000000000000000000018de35c669",
        "valueBefore": "0x0000000000000000000000000000000000000000000000000000001907efdfad",
        "valueBeforeStatus": "resolved",
        "callPath": "00000000",
        "callDepth": 2,
        "callType": "delegatecall"
      },
      {
        "writeIndex": 1,
        "writeIndexStatus": "present",
        "storageAddress": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
        "executionAddress": "0x43506849d7c04f9138d1a2050bbf3a0c054402dd",
        "callerAddress": "0x978e75381d64fb18af7112e42fa76a211a773456",
        "storageKey": "0x995f8903a930b1943e02e2dfd5e2735613745e48d63899f95cc3b0a02df45267",
        "newValue": "0x0000000000000000000000000000000000000000000000000000000029ba1944",
        "valueBefore": "0x0000000000000000000000000000000000000000000000000000000000000000",
        "valueBeforeStatus": "resolved",
        "callPath": "00000000",
        "callDepth": 2,
        "callType": "delegatecall"
      }
    ],
    "writesTruncated": false
  },
  "meta": {
    "chain": "ethereum",
    "timestamp": 1790540650866,
    "cached": false,
    "asOfBlock": 25920000,
    "docs": "https://docs.tracefast.xyz/api/transaction-storage-writes",
    "coverage": {
      "storageWritesFromBlock": 49018,
      "storageWritesThroughBlock": 26071062
    }
  }
}

The storage is the USDC proxy's; the code that wrote it is the implementation, 0x4350…02dd. The sender's slot went down by the amount sent; the recipient's went from zero to the same amount.

data

A write

meta.coverage

Pagination

Pages are keyset, not offset. Pass nextCursor back as cursor until it is absent; keep the same hash. A cursor opens only for this method and this transaction; any other use, or a cursor altered in transit, answers 400 invalid_cursor — restart from the first page. See pagination.

Errors

The last refusal, for a transaction in block 25948983:

{
  "error": {
    "code": "block_not_available",
    "details": {
      "coverageGapFromBlock": 25925129,
      "maxAvailableBlock": 25925128,
      "reason": "coverage_gap"
    },
    "message": "the storage writes of this transaction are not available yet: they are available up to block 25925128. This says nothing about what the transaction wrote — retry later, or ask about a transaction at or below block 25925128.",
    "requestId": "01a08cba-809b-73e1-8700-e53656d3f718"
  }
}

It says nothing about the transaction's outcome or what it wrote; ask again later, or ask about a transaction at or below maxAvailableBlock.

Malformed input, unknown parameters and the key check's 401/403/429 are the same for every method — see conventions and API keys.

Related pages

• Execution trace of a transaction — the frames these writes belong to
• Call frames of a transaction, paged — every frame with its calldata and logs
• Balance of one token on an address — a balance read straight from token storage
• Storage Analytics — storage-write activity across the network, in the app

Last updated 22 Oct 2026, 08:06 UTC · verified against TraceFast v1.0.261 · Markdown