Optimism gas price. Current gas price on Optimism (eth_gasPrice): gas price, base fee and suggested priority fee in gwei, plus what a plain ETH transfer (21,000 gas) costs right now. Takes no input. Use before sending a transaction or to decide whether to wait; for the fee a past transaction actually paid use op_receipt.

HMAC signature. Compute an HMAC of a message with a key using SHA-256 (default), SHA-1, SHA-384 or SHA-512, in hex and base64. Use to check webhook signatures. The key is used only for this call and is not stored.

Signature verify, EIP-191. Verify an Ethereum personal_sign (EIP-191) signature: recover the address that signed a message and, given an expected address, say whether it matches. Works for ordinary wallets (EOAs); smart-contract wallets sign by ERC-1271, which this offline check does not cover. Use for sign-in-with-wallet, proving wallet ownership or checking a signed order. A malformed signature is 400, uncharged.

Token allowance, Optimism ERC-20. ERC-20 token allowance on Optimism: how much a spender may move from an owner's wallet (allowance), raw and in token units, and whether the approval is unlimited. Use to check an approval before a swap or to audit risky open approvals; for the owner's balance use op_token_balance. Token is a ticker (USDC, USDT, WETH…) or a 0x contract; a missing contract is 404 and a non-ERC-20 422, both uncharged.

Estimate gas, Optimism. Estimate the gas a transaction would use on Optimism (eth_estimateGas) and what it would cost at the current gas price, in gas units, gwei and ETH. Give to, plus value in ETH and calldata for a contract call, and the sender when the call depends on it. Use before sending a transaction or to price a batch; for the gas price alone use op_gas. A transaction that would revert is 422 with the reason, uncharged.

Optimism native balance. Native ETH balance (eth_getBalance) of any 0x wallet address on Optimism at the latest block, in wei and in ETH. Use to check whether a wallet can pay gas or a transfer; for ERC-20 tokens use op_token_balance, for all holdings at once use wallet_portfolio. A malformed address is rejected with 400, uncharged.

Number to English words. Write a whole number (up to trillions, negatives allowed) out in English words, e.g. for cheques and invoices. Also returns the cheque form with 'and' cents when given a decimal amount. Use when amounts must be written out in full.

CIDR calculator. Details of an IPv4 network in CIDR notation: network and broadcast address, first and last usable host, netmask, number of addresses, and whether a given IP falls inside. Use for firewall rules and allowlists.

Optimism recent event logs. Recent contract event logs on Optimism (eth_getLogs): the events a contract emitted over the last N blocks (1-1,000, default 50), optionally filtered by topic0 (the 0x 32-byte event signature hash). Returns up to 100 logs with block, transaction hash and topics. Use to watch transfers or contract events; for one transaction's outcome use op_receipt.

Optimism transaction receipt. Transaction receipt on Optimism (eth_getTransactionReceipt): success or reverted, gas used, effective gas price, fee paid in ETH, number of event logs and any contract created. Use to confirm a payment or call went through; for sender, value and calldata use op_tx. Input is a 0x-prefixed 64-hex hash; a pending or unknown hash returns 404, uncharged.

Storage slot read, Optimism. Read one raw storage slot of a contract on Optimism (eth_getStorageAt): the 32-byte word, as a number and, when it holds one, as an address. Slot is a decimal index or a 0x 32-byte key (mapping and proxy slots). Use to inspect contract state that has no getter, owners or implementation pointers; for proxies use op_proxy. A malformed address or slot is rejected with 400, uncharged.

String utilities. Transform one string every common way at once: camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, dot.case, path/case, Title Case, Sentence case, upper and lower; a URL slug (accents removed); reversed; trimmed and whitespace-collapsed; and counts of characters, letters, digits, words and lines. Splits identifiers like userIDValue or XMLHttpRequest correctly. Use when naming fields, files and routes or cleaning user input.

NFT balance, Optimism. How many NFTs of one ERC-721 collection a wallet holds on Optimism (balanceOf), with the collection's name and symbol. Use to check a holder before a token-gated action or to see whether a wallet still holds a collection; for who holds one token id use op_nft_owner. Both inputs are 0x addresses; a missing contract is 404, a contract that is not ERC-721 422, both uncharged.

NFT owner, Optimism. Owner of an NFT on Optimism: the wallet that holds one ERC-721 token id right now (ownerOf), plus the collection's name and symbol. Use to verify who holds an NFT before a trade, a mint gate or an airdrop; for how many a wallet holds use op_nft_balance, for the token's metadata op_nft_metadata. A missing contract is 404, a token that does not exist 422, both uncharged.

Optimism transaction. Look up an Optimism transaction by hash: sender, recipient, value in ETH, nonce, gas limit, the 4-byte function selector and its block. Use to see what was sent or whether it exists; for success or failure and fees paid use op_receipt, for emitted events op_logs. Input is a 0x-prefixed 64-hex hash; an unknown hash returns 404, uncharged.

ID generator, UUID, ULID. Generate unique IDs of every common kind in one call: UUID v4 (random), UUID v7 and ULID (time-ordered, sort by creation), NanoID (21 URL-safe characters) and random base62 and hex strings, up to 20 of each, from the platform's cryptographic random source; and decode the creation time hidden in a ULID or UUID v7. Use for database keys, request and trace IDs, file names or test data.

Optimism ERC-20 balance. ERC-20 token balance of a wallet on Optimism (USDC, USDT, WETH or any token, via balanceOf): raw amount, decimals, symbol and the human-readable amount, live from the token contract. Use to check stablecoin or token holdings before a transfer or trade; for the native coin use op_balance. Both inputs are 0x addresses (40 hex characters); no contract returns 404 and a non-ERC-20 contract 422, both uncharged.

Optimism ERC-20 token info. Look up the name, symbol, decimals and total supply of an ERC-20 token contract on Optimism, live from the contract. Use to identify an unknown token address or to format raw amounts; for a holder's balance use op_token_balance. Input is a ticker (USDC, WETH…) or the token's 0x contract address; an address that is not an ERC-20 contract returns 422, uncharged.

Proxy implementation, Optimism. Find the implementation behind a proxy contract on Optimism: reads the EIP-1967 implementation, beacon and admin slots, EIP-1822 (UUPS), the older OpenZeppelin layout and EIP-1167 minimal-proxy bytecode, and names the kind found. Use before trusting or decoding a contract whose code can be swapped by its admin; for a fuller risk verdict use contract_risk. A malformed address is 400; an address without code is 404, both uncharged.

NFT metadata, Optimism. NFT metadata on Optimism: the token URI of one ERC-721 token id (tokenURI) and the JSON it points to (name, description, image, attributes), read from data: URIs, https or ipfs:// (through ipfs.io). Strings over 1,000 characters, such as on-chain SVG images, are shortened. Use to show or check what an NFT is; for its owner use op_nft_owner. A token that does not exist is 422, uncharged; unreachable metadata is reported in metadataError.