Prefill the Simulator with a draft link

A draft link opens the Tenderly Simulator with a pre-filled form. Nothing runs until the recipient clicks Simulate, so the link is safe to share in test reports, pull requests, or alerts. A draft prefills a single simulation, not a bundle. It populates one transaction form (one row); it does not reconstruct a multi-step bundle.

URL format

The link is the Simulator’s new-simulation route with a draft query parameter: https://dashboard.tenderly.co/<org>/<project>/simulator/new?draft=<value> <value> is the draft JSON payload, UTF-8 encoded, then base64url: standard base64 with + replaced by -, / replaced by _, and = padding stripped.

For a one-off share you do not need a script. Fill the form in the Simulator and click Copy draft link in the page header (shown while the bundle has a single simulation). The rest of this page is for generating links programmatically, from CI, test reports, or other tooling.

Quick start

A minimal raw-calldata draft is all most CI scripts need. The to address goes in contractAddress, and the calldata goes in rawFunctionInput:

{
  "v": 1,
  "network": { "id": "1" },
  "row": {
    "contractAddress": "0xdac17f958d2ee523a2206206994597c13d831ec7",
    "from": "0xab5801a7d398351b8be11c439e05c5b3259aec9b",
    "inputDataType": "raw",
    "rawFunctionInput": "0xa9059cbb…"
  }
}

Encode that payload and append it to the URL:

import base64, json

payload = {
    "v": 1,
    "network": {"id": "1"},
    "row": {
        "contractAddress": "0xdac17f958d2ee523a2206206994597c13d831ec7",
        "from": "0xab5801a7d398351b8be11c439e05c5b3259aec9b",
        "inputDataType": "raw",
        "rawFunctionInput": "0xa9059cbb…",
    },
}

draft = base64.urlsafe_b64encode(json.dumps(payload).encode()).decode().rstrip("=")
url = f"https://dashboard.tenderly.co/<org>/<project>/simulator/new?draft={draft}"

// Node.js
const payload = {
  v: 1,
  network: { id: "1" },
  row: {
    contractAddress: "0xdac17f958d2ee523a2206206994597c13d831ec7",
    from: "0xab5801a7d398351b8be11c439e05c5b3259aec9b",
    inputDataType: "raw",
    rawFunctionInput: "0xa9059cbb…",
  },
};

const draft = Buffer.from(JSON.stringify(payload)).toString("base64url");
const url = `https://dashboard.tenderly.co/<org>/<project>/simulator/new?draft=${draft}`;

# Shell, reading the payload from payload.json (GNU coreutils)
DRAFT=$(jq -c . payload.json | basenc --base64url -w0 | tr -d '=')
# macOS fallback:
DRAFT=$(jq -c . payload.json | base64 | tr '+/' '-_' | tr -d '=\n')

Top-level payload

Field	Type	Required	Description
`v`	number	yes	Schema version. Must be `1`.
`network`	`{ "id": string }` or `null`	yes	Chain id as a string (`"1"` is Mainnet, `"56"` is BNB Chain, and so on). Must be a network enabled on the recipient’s project, otherwise they get a “network not available” error and an empty form. Always set it. `null` is accepted but skips the contract lookup and leaves the form mostly unusable. See Supported Networks for chain ids.
`row`	object	yes	The form fields. See `row` fields below.

`row` fields

Only contractAddress is required. Omit anything you do not need. Omitted fields keep the form’s defaults, and unknown extra fields are ignored.

Contract and function

Field	Type	Description
`contractAddress`	string	Required. The “to” address. The contract and its ABI are fetched on the recipient’s side when the link opens.
`inputDataType`	`"decoded"` or `"raw"`	Selects the function-input mode. Use `"raw"` with `rawFunctionInput`, or `"decoded"` with `contractFunction` and `functionInputs`.
`rawFunctionInput`	string	Hex calldata (`0x…`) for raw mode. No ABI needed, which makes it the most robust option for scripts.
`contractFunction`	object or `null`	Decoded-mode function reference: `{ "name": string, "selector"?: string, "signature"?: string }`. `name` is required inside the object. `selector` (4-byte hex, e.g. `"0xa9059cbb"`) is optional but preferred: it is matched first and is exact for overloaded functions. Without it, matching falls back to `name` and may pick the wrong overload. `signature` is informational only.
`functionInputs`	array or object	Decoded-mode argument values. Preferred: a positional array in ABI order, for example `["0xabc…", "1000000", ["0xa…", "0xb…"]]`. Values are strings, numbers, or booleans. Array and tuple arguments may be passed natively as nested arrays or objects, with no pre-stringifying needed. The keyed form `{ "input_0": … }` is also accepted (it is what the UI’s Copy button emits).
`contractAbiImport`	string	Pre-fills the in-app “Edit ABI” field. Function matching on open uses the fetched ABI only, so this field does not make decoded mode work for unverified contracts. Use raw calldata for those.

Transaction parameters

Field	Type	Description
`from`	string	Sender address.
`gas`	string or number	Gas limit, e.g. `"8000000"`.
`gasPrice`	string or number	Gas price in wei.
`value`	string or number	Native-token value in wei.

Block selection

Field	Type	Description
`block`	string or number	Block number to simulate at. Omit for the chain head.
`blockIndex`	string, number, or `null`	Transaction position inside the block. `null` or omitted means the start of the block.
`endOfBlock`	boolean	`true` runs the simulated transaction after every transaction in the block (overrides `blockIndex`).
`usePendingBlock`	boolean	`true` simulates on the pending block instead of a fixed number.

See Simulation Parameters for how block selection and transaction index behave in the UI.

L2 parameters

These fields apply to OP-stack and Boba networks only.

Field	Type	Description
`depositTx`	boolean	Mark as an L2 deposit transaction.
`systemTx`	boolean	Mark as an L2 system transaction.
`mint`	string	Deposit mint amount.
`l1BlockNumber`	string	Originating L1 block number.
`l1Timestamp`	string	Originating L1 timestamp.
`l1MessageSender`	string	L1 message sender address.
`l1Turing`	string	Boba Turing data.

Overrides

Field	Type	Description
`blockHeaderOverrides`	object	`{ "number"?: …, "timestamp"?: … }`, each a string, number, or `null`. Overrides the simulated block header.
`stateOverrides`	array	Per-contract state overrides: `{ "id"?: string, "contractAddress": string, "balance": string, "storage"?: [{ "key": string, "value": string }], "code"?: string }`. `id` is optional and generated when absent. `balance` is in wei (`""` means no balance override). `storage` keys and values are 32-byte hex.
`accessList`	array	EIP-2930 access list: `{ "address": string, "storageKeys": string[] }`.

Two override types are UI-only and cannot be set in a draft. Configure them in the app after opening the link: fund-address ERC-20 overrides and custom Solidity sources (the in-app “Edit source” feature).

Validation

Draft hydration is all-or-nothing. A missing required field, a wrong v, or any wrong-typed field rejects the whole payload: the recipient sees “This draft link is invalid or corrupted” and an empty form. There is no partial hydration, so a broken script fails visibly instead of half-working.

Limits and tips

Keep the final URL under 2000 characters. The app refuses to copy longer links, and browsers and proxies may truncate them. Decoded calls with many inputs land around ~1900.
Discovering payload shapes: fill the form in the Simulator UI, click Copy draft link, and base64url-decode the draft value. The result is a known-good payload for your exact use case, and it is the best way to get the advanced shapes (stateOverrides, accessList) right.
The contract ABI is fetched when the link opens. If it cannot be resolved (an unverified contract), decoded-mode drafts open with the address filled but no function selected. Raw mode is immune to this.

For the form fields a draft populates, see Simulation Parameters. To keep a modified state as a persistent environment instead of a one-shot simulation, use Virtual Environments.

Getting Started

Simulator

Console

Monitor

Node RPC

Account & Settings

Prefill the Simulator with a draft link

URL format

Quick start

Top-level payload

`row` fields

Contract and function

Transaction parameters

Block selection

L2 parameters

Overrides

Validation

Limits and tips

​URL format

​Quick start

​Top-level payload

​row fields

​Contract and function

​Transaction parameters

​Block selection

​L2 parameters

​Overrides

​Validation

​Limits and tips

URL format

Quick start

Top-level payload

`row` fields

Contract and function

Transaction parameters

Block selection

L2 parameters

Overrides

Validation

Limits and tips