Where are 'transaction ids' visible'
There are several providers giving you the possibility to explore the Blockchain. As the most cryptocurrencies are pulic Blockchains all transactions made on it are publicly visible and accessible for everyone at any time.
The most popular providers:
https://etherscan.io – For Ether transactions or ERC-20 tokens
https://www.blockchain.com/explorer – For Bitcoin transactions
https://xrpcharts.ripple.com/#/ – For Ripple transactions