# Ethereum address from key

Derive Ethereum 0x addresses and EIP-55 checksum casing from secp256k1 private-key or public-key hex, fully locally.

## Run it

- **CLI:** `gizza tool eth-address-from-key "0000000000000000000000000000000000000000000000000000000000000001"`
- **Web:** https://gizza.ai/tools/eth-address-from-key/
- **Agents:** machine-readable descriptor (parameters JSON Schema) at https://gizza.ai/tools/eth-address-from-key/tool.json

## Inputs

- `key` — Private or public key hex _(field)_
- `key_type` — Key type _(field)_
- `output_format` — Output format _(field)_

## Output

- Ethereum address (text)

## Query parameters

Open the tool pre-filled and auto-run via URL:

- `key` — Private or public key hex
- `key_type` — Key type
- `output_format` — Output format

Example: `https://gizza.ai/tools/eth-address-from-key/?key=0000000000000000000000000000000000000000000000000000000000000001&key_type=auto&output_format=all`

---

## About this tool

Ethereum account addresses are derived from secp256k1 public keys. Starting with a private key, the public key is first computed on the secp256k1 curve. Starting with a public key, the key is decoded from compressed SEC1, uncompressed SEC1, or raw `x || y` bytes. The Ethereum address is then the last 20 bytes of `Keccak-256(uncompressed_public_key_without_the_04_prefix)`.

The checksum form is EIP-55: take the lowercase 40-hex-character address, hash those ASCII hex characters with Keccak-256, and uppercase each address nibble whose matching hash nibble is 8 or higher. For the canonical private key `0000000000000000000000000000000000000000000000000000000000000001`, the checksum address is:

```
0x7E5F4552091A69125d5DfCb7b8C2659029395Bdf
```

Choose **All fields** if you want the checksum address plus the lowercase address, bare no-prefix form, and the compressed/uncompressed public keys. Choose **JSON** when piping the output into another script.

Limits and edge cases: this is a deterministic address derivation tool, not a wallet. It does not generate entropy, sign transactions, query balances, validate ownership, or accept mnemonics, keystore JSON, WIF, or xpub values. Private keys must be exactly 32 bytes and valid secp256k1 scalars. Public keys must be valid curve points encoded as 33-byte compressed SEC1, 65-byte uncompressed SEC1, or 64-byte raw `x || y` hex. A leading `0x` is accepted, and whitespace, underscores, colons, and hyphens are ignored for paste-friendly formatting.

## FAQ

<details>
<summary>Does this send my private key anywhere?</summary>

No. The page runs the same WebAssembly code in your browser that the CLI runs locally. The key is used only to derive the public key and address; nothing is uploaded, stored, or looked up on-chain.

</details>

<details>
<summary>Can I paste a public key instead of a private key?</summary>

Yes. Use **Auto-detect** or **Public key** and paste a compressed public key beginning with `02` or `03`, an uncompressed SEC1 public key beginning with `04`, or the raw 64-byte `x || y` public-key coordinates. All three forms derive the same Ethereum address when they describe the same point.

</details>

<details>
<summary>Why is the checksum address mixed-case?</summary>

EIP-55 encodes a checksum in the letter casing of the hexadecimal address. Wallets can use that casing to catch many mistyped addresses while preserving compatibility with systems that compare addresses case-insensitively after lowercasing.

</details>

<details>
<summary>Is this the same as a Bitcoin address from the same key?</summary>

No. The secp256k1 public key point is the same, but Ethereum uses Keccak-256 and keeps the last 20 bytes directly as a `0x` address. Bitcoin uses HASH160 plus network/version bytes and Base58Check or Bech32 encoding. Use a Bitcoin-specific address tool for those formats.

</details>

## Related tools

- [Keccak-256 Hash Generator](https://gizza.ai/tools/keccak-hash/): Compute the original Keccak-256 or Keccak-512 hash of any text in your browser — the exact hash Ethereum uses, not FIPS SHA-3. Free and private.
- [secp256k1 Public Key Derivation](https://gizza.ai/tools/secp256k1-pubkey-derive/): Derive the secp256k1 public key from a private key: compressed (02/03) and uncompressed (04) SEC1 points, plus X and Y coordinates. Hex or WIF input, all in your browser.
- [SM2 public key from private key](https://gizza.ai/tools/sm2-public-from-private/): Derive an SM2 public key from a private key (GM/T 0003, curve sm2p256v1) — hex scalar or PKCS#8 PEM in, SEC1 hex and SPKI PEM out. In-browser, no upload.
- [Age Key Generator](https://gizza.ai/tools/age-keygen/): Generate an age X25519 identity and its shareable age1 public recipient in your browser, or derive the recipient from an identity you already have.
- [Bitcoin Address Tool](https://gizza.ai/tools/bitcoin-address/): Derive Bitcoin P2PKH, P2SH-P2WPKH, P2WPKH addresses and WIF from a secp256k1 private key. Supports hex or WIF input, mainnet and testnet.