CoinMarketCap is a great resource for looking up spot prices and historical data for the top coins on the market. They aggregate prices from hundreds of different exchanges and then compute a "price index" for each coin based on a volume-weighted average. They are best-in-class at doing this! The reason I am deducting one star is that they actively de-list coins from their service without notice. I'm not sure what the criteria is for doing this, but it makes things especially problematic for app developers like me who rely on their public API for price and supply information. The endpoints we use to query data break all the time, and there's not much we can do about it right now other than use a different (more stable) source for the data, like CryptoCompare. We're also facing rate-limiting issues with the CoinMarketCap API, but this will hopefully be addressed with their upcoming paid API option. We've been eagerly waiting for this, but we're just not sure when exactly it will be released.