As an AI language model, I can provide you with the top 10 cryptocurrencies by market capitalization as of September 2021. However, please note that the cryptocurrency market is highly volatile and positions can change rapidly. Here are the top 10 cryptocurrencies at the time of writing:
1. Bitcoin (BTC)
2. Ethereum (ETH)
3. Binance Coin (BNB)
4. Tether (USDT)
5. Cardano (ADA)
6. XRP (Ripple)
7. Solana (SOL)
8. Polkadot (DOT)
9. Dogecoin (DOGE)
10. USD Coin (USDC)
Please keep in mind that the aforementioned rankings are subject to change over time as the market fluctuates. It is always a good idea to verify the current market capitalization of cryptocurrencies through reliable sources before making any investment decisions.