Wallet Address Checksum: Verify and Revoke Approvals

Quick answer

A wallet address checksum (EIP-55) encodes the address in mixed case so a single mistyped character is rejected before you send funds. ChainSignal’s free Address Checksum & Revoke Tracker both generates the EIP-55 checksum for any 0x address and scans ERC-20 approvals across five chains. It is read-only, uses public RPC, and never asks for a private key.

What a wallet address checksum (EIP-55) is

Ethereum addresses are 20-byte values, normally written as 40 hexadecimal characters after a 0x prefix. In their raw form they are case-insensitive, which means a typo — swapping one character for another — produces a different but still valid-looking address. If you send funds there, they are gone.

The wallet address checksum defined by EIP-55 solves this by using the case of each letter to carry extra information. The standard takes the Keccak-256 hash of the lowercase address and uses it to decide which letters become uppercase. The result is a mixed-case address where any single character error changes the hash pattern and fails validation. The checksum therefore catches typos at the moment you paste or compare an address.

Why mixed case catches typos

If you type 0x followed by 40 hex chars, the computer cannot know you meant a different letter. But with EIP-55, the uppercase and lowercase letters are not decorative — they are a mathematical fingerprint of the correct address. Change one character and the fingerprint no longer matches, so a compliant wallet or tool flags it as invalid. That is the entire safety mechanism, and it costs nothing to use.

How the checksum generator tool works

ChainSignal’s checksum generator at chaindepin.com/depin/address-checksum/ is pure client-side logic — the address never leaves your browser. You paste any 0x address and the tool returns the mixed-case EIP-55 form.

What input state the tool reports

The tool does more than output a checksum; it tells you the state of what you pasted:

• All-lowercase — valid as raw hex but carries no checksum protection; the tool supplies the corrected mixed-case form.
• All-uppercase — also unprotected; corrected to mixed case.
• Already valid checksum — the address you pasted is correctly checksummed and passes validation.
• Invalid — the characters do not form a valid EIP-55 address, so something is wrong and you should not use it.

This feedback matters because many copy-pasted addresses arrive in all-lowercase from explorers or spreadsheets, silently losing their typo protection. Running them through a wallet address checksum tool restores that protection before any transaction.

What token approvals (allowances) are

When you interact with a DeFi app — a swap, a lending market, or a staking contract — you usually grant it permission to move a specific token from your wallet. That permission is an ERC-20 “allowance” stored on-chain. The app becomes a spender, and your wallet records how much it may take.

Most interfaces request an “unlimited” approval by default. Instead of approving exactly the amount you trade, the contract is allowed to spend everything, now and in the future. That is convenient, but it means the contract (and the private key that controls it) could drain that token from your wallet at any time, even months later.

Why unlimited ERC-20 approvals are a risk

An unlimited approval is only as safe as the contract it targets. If that contract is exploited, deprecated, or simply malicious, the spender can move the approved token without your further consent. Two names come up constantly in allowance audits:

• Uniswap Universal Router — the modern Uniswap routing contract that many swaps approve.
• Permit2 — Uniswap’s permit system that lets approvals be managed and shared efficiently.

These are widely used and generally reputable, but the principle holds: every approval is a standing permission. The safer habit is to approve only the amount you need, and to revoke approvals you no longer use. You can learn the mechanics of revoking at revoke.cash, a well-known public allowance manager.

How the allowance checker scans five chains

ChainSignal’s allowance checker is the second half of the Address Checksum & Revoke Tracker. You enter a wallet address and it scans that address’s ERC-20 approvals across five chains: Ethereum, Arbitrum, Base, Optimism, and Polygon. It looks specifically for risky or notable spenders such as the Uniswap Universal Router and Permit2, then explains how to revoke them.

Read-only by design

The checker is read-only. It queries public RPC endpoints (via publicnode) to read on-chain approvals; it never requests your private key, seed phrase, or a signature that could move funds. You can safely paste any address to inspect its allowances. If a tool ever asks for your private key to “check” approvals, stop — that is a red flag.

What each chain lets you scan

Different networks carry different tokens and apps, so the risk surface varies. The table below summarizes, per chain, what you can scan and what you risk by ignoring it. The risk column is a general description of the consequences, not a statement of any specific exploit.

Scanning all five takes one address entry, which is far easier than checking each chain’s explorer by hand.

Revoking approvals safely

Revoking is simply setting an approval back to zero (or to the amount you actually want). The ChainSignal tool explains how, and revoke.cash provides a direct interface for it. The safe steps are consistent across tools:

1. Inspect first with a read-only checker — no private key needed.
2. Identify the spenders you no longer use, especially unlimited ones to routers or Permit2.
3. Revoke from your own wallet, paying the network fee to send the zero-approval transaction.
4. Re-approve only when needed, and prefer exact amounts over unlimited.

The wallet address checksum step and the revoke step complement each other: verifying the address prevents sending to the wrong place, while revoking keeps approved contracts from taking more than you intended.

Why the tool never needs your private key

A read-only scan only reads public blockchain state, which is visible to anyone. Because no spend is requested, no signing is required, so no private key is ever involved. This is the correct design for any safety checker, and it is why you can use the ChainSignal tool without fear of exposing credentials.

Make checksum and revoke checks a habit

A good routine: before sending to a new address, run it through a wallet address checksum tool to confirm it is valid and correctly cased. Periodically — say monthly — scan your active wallets for stale approvals across the five supported chains and revoke what you no longer use. These two free, no-login steps remove two of the most common self-inflicted crypto losses: sending to a typo’d address and leaving old approvals open.

Both checks are bundled with the broader ChainSignal DePIN Dashboard, which also tracks eight DePIN networks and offers three other utility tools, all without an account.

Frequently asked questions

What is a wallet address checksum?

A wallet address checksum is the EIP-55 encoding that writes an Ethereum address in mixed case so a typo is detectable. It uses the Keccak-256 hash of the address to decide which letters are uppercase, creating a fingerprint. Any single character error breaks the fingerprint and the address fails validation. This catches mistakes before funds are sent to the wrong place.

How does EIP-55 catch a mistyped character?

EIP-55 derives the uppercase/lowercase pattern from the address’s own hash, so the casing is not arbitrary. If you change even one character, the computed hash no longer matches the required pattern, and a compliant tool flags the address as invalid. The checker at chaindepin.com/depin/address-checksum/ reports whether your input is already valid, lowercase, uppercase, or invalid.

What are ERC-20 token approvals?

ERC-20 approvals are on-chain permissions that let a contract spend a token from your wallet, usually granted when you use a DeFi app. Many interfaces request unlimited approval by default, allowing the spender to take any amount, now or later. If that contract is compromised, it could move the approved token without further consent, which is why periodic review matters.

Why are Uniswap Universal Router and Permit2 mentioned?

The Uniswap Universal Router and Permit2 are common spenders that wallets approve during swaps, so they appear frequently in allowance scans. They are widely used and generally reputable, but every approval is a standing permission. The ChainSignal checker highlights them so you can decide whether each approval is still necessary and revoke the ones you no longer use.

Which chains does the allowance checker support?

The allowance checker scans five chains: Ethereum, Arbitrum, Base, Optimism, and Polygon. It reads ERC-20 approvals on each and flags notable or risky spenders. You enter one address and the tool queries public RPC endpoints across all five, which is far faster than checking each chain’s explorer manually.

Is the ChainSignal checksum and revoke tool safe to use?

Yes, it is read-only and client-side where relevant. The checksum generator runs in your browser and the allowance checker uses public RPC to read on-chain state; neither asks for your private key or seed phrase. You should never share your private key with any checker. If a tool requests it to “scan” approvals, that is a red flag and you should stop.

How do I actually revoke a token approval?

Revoking means sending a transaction that sets the spender’s allowance back to zero, which you do from your own wallet and pay a small network fee for. The ChainSignal tool explains the process, and revoke.cash offers a direct interface. After revoking, re-approve only the exact amount you need for a specific action rather than granting unlimited approvals.

Verifying addresses and auditing approvals are two free habits that prevent the most common avoidable losses. Both live alongside live network data on the ChainSignal DePIN Dashboard.

This is not financial advice. Figures and tool behavior verified October 2026.

Check your own addresses and approvals for free at chaindepin.com/depin/.