1,000 free simulations / month

The ultimate simulation engine
for the onchain economy.

Preview any transaction before it hits the chain.
Token flows, gas costs, state changes — one API call, any EVM chain.

Get API Key Read the Docs

Ethereum

312ms

Uniswap V4 · Mint CLP position

Balance injected Approval added

0x88316456000000000000000000000000a0b86991c6218b36c1d19d4a2e9eb0ce3606eb48000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc200000000000000000000000000000000000000000000000000000000000001f4

Simulation successful

Block #21,847,293

You send

USD Coin USDC ERC20

0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48

−4,217.39

$4,217.39

Wrapped Ether WETH ERC20

0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2

−1.5000

$4,192.50

You receive

Uniswap v4 Positions NFT ERC721

#1,207,888

0xbd216513d74c8cf14cf4747e6aaa6420ff64ee9e

~$8,409.89

Trusted by teams building

DEX Aggregators

Wallets

Yield Protocols

AI Agents

Protocol Frontends

Security Tools

How It Works

From calldata to clarity.

You bring the calldata. We execute it against live chain state and return structured results your UI can render directly.

Send your calldata

POST your transaction — from, to, data, value — and the target chain. That's it.

We simulate it

Executed on a fresh fork of live state. Balance injected, approval prepended, gas computed.

Get structured results

Token amounts, NFT positions, directions, standard types, names, symbols, decimals, gas cost, and human-readable errors.

Why Simulate

Real execution.
Zero requirements.

Your transaction runs on an isolated fork of live chain state — exactly as it would execute on-chain. No setup needed.

✓No wallet connection needed

✓No token balance needed

✓No approval transaction needed

✓No gas funding needed

✓Executes exactly like the real transaction

✓Isolated forked state per request

Transaction Simulator

See everything a transaction does.

Replay any historical transaction or simulate a new one. Get the full execution trace, decoded state changes, token flows, and gas profiling — all in one view.

Ethereum

247ms

swapExactTokensForTokens Balance injected

Network Ethereum

Status Success

From 0xd8dA...6045 vitalik.eth

Gas Used 142,891 $2.14

Token Transfers 3

USD Coin USDC ERC-20

0xA0b8...eB48

−1,500.000000

$1,500.00

Wrapped Ether WETH ERC-20

0xC02a...6Cc2

+0.535000

$1,498.42

Execution Trace

Events

Addresses

State Changes

▼ CALL 142,891 100% UniswapV2Router02.swapExactTokensForTokens(1500000000, 0, [0xA0b8...eB48, 0xC02a...6Cc2], 0xd8dA...6045, 1711929600)

▼ CALL 118,432 82.9% UniswapV2Pair.swap(0, 535000000000000000, 0xd8dA...6045, 0x)

▶ CALL 12,891 9.0% WETH.transfer(0xd8dA...6045, 535000000000000000) → true

▶ CALL 9,342 6.5% USDC.transfer(0x7a25...488D, 1500000000) → true

▶ STATICCALL 812 0.6% UniswapV2Factory.getReserves() → (1204500000000, 429850000000000000000)

State Changes · Events · Addresses — explore more →

Full Execution Trace

Decoded call tree with collapsible depth, contract names, and function signatures at every level.

Storage State Diffs

Variable names, types, before/after values, and mapping key grouping for every slot touched.

Token Transfers & Pricing

Every token flow with amounts and USD values at transaction time or current prices.

Gas Profiling

Per-function gas breakdown as a percentage of total execution cost with flame chart visualization.

Auto ABI Resolution

Sourcify, Etherscan, and EVMole bytecode analysis for automatic function decoding.

27 Chains Supported

Ethereum, Base, Arbitrum, Polygon, Optimism, and 22 more EVM networks.

Signature-Gate Bypass

Safe multisigs, ERC-20 permits, ERC-4337 UserOps, and EIP-7702 delegates all simulate without real signatures.

Balance & Approval Injection

Simulate swaps without holding the token or pre-approving the spender — balances and allowances are set for you.

Historical Re-Simulation

Pin any past block and replay a transaction exactly as it originally executed — deterministic to the slot.

Paste a transaction hash or build a simulation from scratch.

Try the Simulator

Use Cases

Know the exact impact before
it hits the chain.

From swap previews to security screening — simulation is the foundation for every DeFi product that takes user experience seriously.

DEX Aggregators & Routers

Show accurate output amounts, gas costs, and token metadata directly in your swap UI. Simulate against live chain state with automatic balance injection — no whale accounts or forked environments required.

Wallets & Portfolio Apps

Give users a clear preview of every transaction before they sign. Display human-readable asset changes for ERC20s, NFTs, and multi-tokens — with token names, amounts, and standard types. Building trust at sign time.

Lending, Yield & CLP Positions

Preview vault deposits, borrow positions, CLP mints, and leverage loops before committing capital. Batch simulation lets you chain supply→borrow→swap in a single call with shared state. Works with Uniswap V3, Aave, Morpho, Pendle, and any EVM protocol.

AI Agents & Automation

Verify transaction outcomes programmatically before execution. Chain multi-step flows with batch simulation — one API call returns structured results for every step.

Smart Contract Development

Test contract interactions against live mainnet state without deploying to a testnet. Validate user flows end-to-end with real token balances, prices, and protocol state.

Transaction Security

Screen transactions for unexpected asset transfers before users approve them. Surface clear warnings with decoded token names and amounts — catch reverts and malicious behavior before they cost gas.

Protocol Coverage

Every DeFi primitive.
Every token standard.

Simulate any transaction across the DeFi stack — from simple token swaps to lending deposits & withdrawals, cross-chain bridge flows, leverage loops, and multi-step vault strategies.

Token Swaps

Lending & Borrowing

Liquid Staking

Yield Vaults

Restaking

CLP Positions

Flash Loans

Leverage Loops

Batch Simulations

ERC721 NFTs

ERC1155 Multi-Token

Yield Tokenization

RWAs

Cross-Chain Bridges

Real-time

Simulation results

API call — that's it

Sub-second

Cached lookups

Uniswap Morpho Aave V3 Pendle Compound Lido Rocket Pool EigenLayer Ethena Euler Yearn V3 Convex Curve Spark Maker Frax ether.fi Silo Beefy Usual Protocol

ERC20s, ERC721 NFTs, ERC1155 multi-tokens, proxy tokens, rebasing tokens, vault shares, LP tokens, PT/YT tokens — every standard works.
CLP positions tracked by tokenId. Lending receipt tokens (aTokens, cTokens, vault shares) automatically handled in batch mode. Cross-chain recipient tracking for bridge flows. Batch simulations chain multi-step flows (supply→borrow→swap) in a single call. If it's an EVM transaction, we can simulate it.

What You Get

Everything in one response.

No chaining APIs, no post-processing, no separate metadata calls.

Automatic balance injection auto

Sender doesn't have tokens? We detect the right approach and inject the balance for the simulation. Works for every ERC20, lending receipt token (aTokens, cTokens), and vault share we've tested — thousands of tokens across 27 chains.

Automatic token approval auto

The approve transaction is prepended automatically. You send the swap calldata, we handle the approval. One less thing to worry about.

Token metadata included included

Every response includes name, symbol, and decimals for all tokens involved. Display "1,234.56 USDC" instead of "1234560000 0xa0b8...".

Multi-standard asset tracking new

ERC20 tokens, ERC721 NFTs, and ERC1155 multi-tokens — all tracked with net direction, tokenId, and standard type. CLP positions, game items, and NFT mints all show up as structured asset changes.

Batch simulations pro

Chain multiple transactions in a single call — supply, borrow, swap, re-supply — all executed in one simulated block with shared state. Get per-step success/failure and aggregated net asset changes.