Blockchain - Bitcoin Block Explorer - Blockchain is popular Bitcoin Legacy (BTC) block explorer.
Blockchair - Bitcoin, BitcoinCash, Ethereum, and Litecoin blockchain search and analytics engine.
Bitcoin.com Explorer - View transactions, addresses, and more on the Bitcoin Cash and Bitcoin Core blockchains.
Infura - Ethereum node as an API
BTC.com - Bitcoin Explorer - BTC.com - Bitcoin block explorer is a BitcoinCash and Bitcoin Legacy (BTC) blockchain explorer.
BeMoreBitcoin Bitcoin Wallet LookUp - The bitcoin wallet address checker allows you to quickly check a wallet address, returning the amount held in the wallet and recent transaction details.