Smart Contracts & EVM Tools

Free online smart contract tools — a Keccak-256 function selector calculator computed entirely client-side. Nothing is ever sent to a server.

6 tools

Function Selector

Compute the 4-byte Ethereum function selector from a Solidity signature using Keccak-256, entirely in your browser. Paste names or types.

Gas Fee Calculator

Calculate Ethereum gas fees in ETH and USD. Supports EIP-1559 (base fee + tip) and legacy gas price. Six transaction type presets included.

ENS Namehash

Compute the ENS namehash (EIP-137) for any .eth domain, label by label, using Keccak-256 in your browser. See every recursive hashing step.

Merkle Tree Builder

Build a Keccak-256 Merkle tree from an address allowlist, read off the root, and copy an inclusion proof for any leaf. OpenZeppelin sorted pairs.

ABI Encoder

Encode a Solidity function call to calldata or decode raw calldata to typed values. Supports uint/int, bool, address, bytesN, bytes and string. No upload.

Also in Smart Contracts & EVM

Tools from other categories tagged with Smart Contracts & EVM

RLP Encoder

Decode a raw Ethereum RLP payload into its fields, or serialise a nested structure back into bytes. Shows every item, length prefix and nesting level.

Why These Tools

Function Selector Calculator and Gas Fee Calculator (EIP-1559) are the first two tools in a category built for Solidity developers. The function selector tool computes the 4 bytes at the front of every contract call using a from-scratch Keccak-256 implementation rather than the browser's built-in SHA-3 — the two use different padding and would silently produce the wrong 4 bytes for every single signature. The gas fee calculator handles the EIP-1559 base-fee-plus-tip model and legacy gas price, shows both the actual and max fee in ETH and USD across six preset transaction types, and uses BigInt arithmetic so there is no floating-point loss at the Wei level. ABI encoding, Merkle proof tooling, and opcode gas references are what is coming next.