WhatsABI Review 2026 | CryptoTools

Name: WhatsABI
Author: WhatsABI

About WhatsABI

WhatsABI is an ABI discovery tool for Ethereum contract review, especially when a contract is unverified or only bytecode is available. It attempts to infer a usable contract interface from bytecode patterns and 4-byte function selectors, helping developers identify likely callable functions before source code or a published ABI is found. Treat its output as a hypothesis, not a source of truth: selector matches can be ambiguous, proxy contracts may expose implementation behavior indirectly, and optimized or unusual bytecode can produce false positives or miss functions. For serious use, verify inferred ABIs against source code, block explorer metadata, verified implementations, event logs, transaction traces, and manual selector checks before integrating with production systems.

What is WhatsABI?

WhatsABI is a tool for ABI discovery and Ethereum contract review. Its main job is to infer likely contract ABIs from deployed bytecode and function selectors when a verified source file or official ABI is missing. This makes it useful for unverified contracts, older deployments, quick selector research, and first-pass interaction planning. The important caveat is that inferred ABIs are probabilistic: identical 4-byte selectors can collide, bytecode patterns can be incomplete, and proxies can make the address you inspect differ from the implementation that actually handles calls. A good WhatsABI review should treat the generated interface as a lead to verify against block explorers, source repositories, verified implementation contracts, traces, logs, and independent selector lookups.

How to Use WhatsABI

Enter the contract address or bytecode you want to inspect, then review the ABI candidates WhatsABI derives from bytecode patterns and 4-byte function selectors.

Separate direct contract findings from proxy-related findings by checking whether the address is a proxy and, if so, locating the current implementation contract.

Compare inferred function names, inputs, outputs, and mutability against verified source code, explorer metadata, selector databases, event logs, and transaction traces.

Flag ambiguous selectors, missing functions, duplicate-looking signatures, and unexpected payable or state-changing calls for manual review before building transactions around them.

Use the inferred ABI for exploration, debugging, or read-only calls first; only move it into automation after source, explorer, or trace-based verification supports the result.

WhatsABI's Core Features

ABI inference from deployed bytecode, useful when the contract is unverified or the published ABI cannot be found.

Function selector discovery from 4-byte selectors, helping reviewers map unknown calldata to likely human-readable signatures.

Fast first-pass interface generation for contract inspection, debugging, read calls, scripts, and explorer-style interaction planning.

Proxy-aware review workflow, where the inferred ABI should be checked against the proxy address, implementation address, and any upgrade history.

Risk-focused validation

false positives, selector collisions, optimized bytecode, fallback routing, and incomplete interfaces all require source, explorer, or trace confirmation.

WhatsABI's Use Cases

Review an unverified Ethereum contract before writing a script, dashboard, bot, or internal tool that needs a usable ABI.

Identify likely function names behind unknown calldata selectors during incident response, protocol research, or wallet transaction analysis.

Generate a temporary ABI for read-only calls while waiting for verified source code, official documentation, or an explorer-published ABI.

Check proxy contracts by comparing inferred interfaces from the proxy and implementation addresses before assuming which functions are callable.

Spot ABI gaps or suspicious selector matches, then verify them with source, explorer metadata, transaction traces, logs, and independent selector databases.

Frequently Asked Questions About WhatsABI

WhatsABI: What developer workflow does it support?

WhatsABI is most useful for ABI discovery during Ethereum contract review. It helps infer a likely interface from bytecode and selectors when a contract is unverified, undocumented, or missing an official ABI.

WhatsABI: How should inferred ABI output be checked?

Start with read-only calls and compare the inferred functions with verified source, block explorer metadata, selector databases, event logs, and transaction traces. Treat each function signature as a candidate until independent evidence supports it.

WhatsABI: What must be checked before production use?

Review false positives, missing functions, selector collisions, proxy routing, implementation upgrades, fallback behavior, and whether function mutability is correct. Production integrations should rely on verified source or trace-backed confirmation, not inference alone.

WhatsABI: Why do proxy contracts need extra care?

A proxy address may contain only routing logic while calls are delegated to an implementation contract. When reviewing a proxy, inspect both addresses, check upgrade history, and verify which implementation handled the transactions you are analyzing.