The top 10 cryptocurrencies by market capitalization in 2021 (as of November 2021) are:
1. Bitcoin (BTC)
2. Ethereum (ETH)
3. Binance Coin (BNB)
4. Tether (USDT)
5. Solana (SOL)
6. Cardano (ADA)
7. XRP (XRP)
8. Dogecoin (DOGE)
9. Polkadot (DOT)
10. USD Coin (USDC)
Please note that the rankings can fluctuate over time based on market conditions and the performance of individual cryptocurrencies.