---
name: onchain-safety
title: Onchain safety checks
summary: Three checks before you sign, buy or send — readable by people and agents.
tags: [onchain, security]
---
# Onchain safety checks

## 1. Read what you are signing
- Function selector `0x095ea7b3` = `approve(spender, amount)`. An amount of `0xfff…fff` is an **unlimited** approval.
- `0xa22cb465` = `setApprovalForAll(operator, true)` — hands over every NFT in a collection.
- EIP-2612 / Permit2 typed-data signatures can move tokens **without a transaction**. Treat a "just a signature" request for `Permit` as a spend.
- When in doubt, approve an exact amount and revoke afterwards.

## 2. Contract red flags (token buyers)
Look for owner-only functions that can: mint after launch, blacklist or block selling, set taxes up to 100%, pause transfers, change the router, or pull tokens from holders. Check whether ownership was renounced and liquidity locked.

## 3. Clean an airdrop list
Validate every address (40 hex chars), convert to EIP-55 checksum, merge duplicates by summing amounts, reject bad lines with a reason, and output `address,amount`.

Our free browser tools do all three: nightshift.fans/#tools — nothing you paste leaves your device (Contract Scan uses your own Claude account).