Here are the 12 most popular types of cryptocurrency by market capitalization as of December 21, 2023 :

1. Bitcoin (BTC): The first major cryptocurrency to hit the market, Bitcoin is still the coin people generally reference when discussing digital currency. Its mysterious creator, Satoshi Nakamoto, debuted the currency in 2009 and has been on a roller-coaster ride since then. As of December 21, 2023, its market cap is $855 billion.

2. Ethereum (ETH): The name for the cryptocurrency platform, Ethereum is the second name you’re most likely to recognize in the crypto space. The system allows you to use ether (the currency) to perform several functions, but the smart contract aspect of Ethereum helps make it a popular currency. As of December 21, 2023, its market cap is $268 billion.

3. Tether (USDT): Tether’s price is $1 per coin. That’s because it is what’s called a stablecoin. Stablecoins are tied to the value of a specific asset, in Tether’s case, the U.S. Dollar. Tether often acts as a medium when traders move from one cryptocurrency to another. Rather than move back to dollars, they use Tether. However, some people are concerned that Tether isn’t safely backed by dollars held in reserve but instead uses a short-term form of unsecured debt. As of December 21, 2023, its market cap is $91 billion.

4. BNB (BNB): BNB is the cryptocurrency issued by Binance, among the largest crypto exchanges in the world. While originally created as a token to pay for discounted trades, Binance Coin can now be used for payments as well as purchasing various goods and services. As of December 21, 2023, its market cap is $41 billion.

5. Solana (SOL): Launched in March 2020, Solana is a newer cryptocurrency and it touts its speed at completing transactions and the overall robustness of its “web-scale” platform. The issuance of the currency, called SOL, is capped at 480 million coins. As of December 21, 2023, its market cap is $37 billion.

6. XRP (XRP): XRP is the cryptocurrency used by Ripple, a company that aims to provide fast, affordable, and reliable cross-border payments. As of December 21, 2023, its market cap is $31 billion.

7. USD Coin (USDC): USDC is another stablecoin, but this one is backed by U.S. dollars held in reserve. As of December 21, 2023, its market cap is $28 billion.

8. Cardano (ADA): Cardano is a blockchain platform that runs the ADA cryptocurrency. The platform is designed to be more energy-efficient than other blockchain platforms, and it’s also designed to be more scalable. As of December 21, 2023, its market cap is $27 billion.

9. Avalanche (AVAX): Avalanche is a newer cryptocurrency platform that aims to provide faster and cheaper transactions than other platforms. As of December 21, 2023, its market cap is $25 billion.

10. Dogecoin (DOGE): Dogecoin started as a joke, but it’s become a popular cryptocurrency in its own right. As of December 21, 2023, its market cap is $22 billion.

11. Polkadot (DOT): Polkadot is a blockchain platform that aims to provide interoperability between different blockchains. As of December 21, 2023, its market cap is $20 billion.

12. Tron (TRX): Tron is a blockchain platform that aims to provide a decentralized platform for content creators. As of December 21, 2023, its market cap is $19 billion.

Please note that the market capitalization of cryptocurrencies is highly volatile and can change rapidly.