---
description: "Fetch the EIP-1967 implementation for a contract Can read from the implementation slot or the beacon slot"
---

_Generated from `cast implementation --help`; see [CLI reference versions](/reference/versions). Regenerate this page instead of editing it directly._

## cast implementation

Fetch the EIP-1967 implementation for a contract Can read from the
implementation slot or the beacon slot

:::terminal

```bash
$ cast implementation --help
```

```txt
Usage: cast implementation [OPTIONS] <WHO>

Arguments:
  <WHO>
          The address for which the implementation will be fetched

Options:
  -B, --block <BLOCK>
          The block height to query at.
          
          Can also be the tags earliest, finalized, safe, latest, or pending.

      --beacon
          Fetch the implementation from the beacon slot.
          
          If not specified, the implementation slot is used.

  -h, --help
          Print help (see a summary with '-h')

  -j, --threads <THREADS>
          Number of threads to use. Specifying 0 defaults to the number of
          logical cores
          
          [alias: --jobs]

      --profile <PROFILE>
          The configuration profile to use

Rpc options:
  -r, --rpc-url <URL>
          The RPC endpoint
          
          [alias: --fork-url]

  -k, --insecure
          Allow insecure RPC connections (accept invalid HTTPS certificates).
          
          When the provider's inner runtime transport variant is HTTP, this
          configures the reqwest client to accept invalid certificates.

      --rpc-timeout <RPC_TIMEOUT>
          Timeout for the RPC request in seconds.
          
          The specified timeout will be used to override the default timeout for
          RPC requests.
          
          Default value: 45
          
          [env: ETH_RPC_TIMEOUT=]

      --no-proxy
          Disable automatic proxy detection.
          
          Use this in sandboxed environments (e.g., Cursor IDE sandbox, macOS
          App Sandbox) where system proxy detection causes crashes. When
          enabled, HTTP_PROXY/HTTPS_PROXY environment variables and system proxy
          settings will be ignored.

      --compute-units-per-second <CUPS>
          Sets the number of assumed available compute units per second for this
          provider.
          
          default value: 330
          
          See also
          [https://docs.alchemy.com/reference/compute-units#what-are-cups-compute-units-per-second](https://docs.alchemy.com/reference/compute-units#what-are-cups-compute-units-per-second)

      --no-rpc-rate-limit
          Disables rate limiting for this node's provider.
          
          See also
          [https://docs.alchemy.com/reference/compute-units#what-are-cups-compute-units-per-second](https://docs.alchemy.com/reference/compute-units#what-are-cups-compute-units-per-second)
          
          [alias: --no-rate-limit]

      --flashbots
          Use the Flashbots RPC URL with fast mode
          ([https://rpc.flashbots.net/fast](https://rpc.flashbots.net/fast)).
          
          This shares the transaction privately with all registered builders.
          
          See:
          [https://docs.flashbots.net/flashbots-protect/quick-start#faster-transactions](https://docs.flashbots.net/flashbots-protect/quick-start#faster-transactions)

      --jwt-secret <JWT_SECRET>
          JWT Secret for the RPC endpoint.
          
          The JWT secret will be used to create a JWT for an RPC. For example,
          the following can be used to simulate a CL `engine_forkchoiceUpdated`
          call:
          
          cast rpc --jwt-secret <JWT_SECRET> engine_forkchoiceUpdatedV2
          '["0x6bb38c26db65749ab6e472080a3d20a2f35776494e72016d1e339593f21c59bc",
          "0x6bb38c26db65749ab6e472080a3d20a2f35776494e72016d1e339593f21c59bc",
          "0x6bb38c26db65749ab6e472080a3d20a2f35776494e72016d1e339593f21c59bc"]'
          
          [env: ETH_RPC_JWT_SECRET=]

      --rpc-headers <RPC_HEADERS>
          Specify custom headers for RPC requests
          
          [env: ETH_RPC_HEADERS=]

      --curl
          Print the equivalent curl command instead of making the RPC request

Display options:
      --color <COLOR>
          The color of the log messages

          Possible values:
          - auto:   Intelligently guess whether to use color output (default)
          - always: Force color output
          - never:  Force disable color output

      --json
          Format log messages as JSON

      --md
          Format log messages as Markdown

  -q, --quiet
          Do not print log messages

  -v, --verbosity...
          Verbosity level of the log messages.
          
          Pass multiple times to increase the verbosity (e.g. -v, -vv, -vvv).
          
          Depending on the context the verbosity levels have different meanings.
          
          For example, the verbosity levels of the EVM are:
          - 2 (-vv): Print logs for all tests.
          - 3 (-vvv): Print execution traces for failing tests.
          - 4 (-vvvv): Print execution traces for all tests, and setup traces
          for failing tests.
          - 5 (-vvvvv): Print execution and setup traces for all tests,
          including storage changes and
            backtraces with line numbers.
```

:::