Someone happened to ask me about copy trading, wanting to know whether to choose fixed amount or fixed percentage.

Actually, both modes have their own reasons; it mainly depends on your trading habits and risk tolerance.

The fixed amount method means you invest a specific amount of money each time, regardless of how large the position of the trader you're copying is.
The advantage of this approach is that you can precisely control the cost of each trade, have a clear understanding, and avoid being suddenly pulled into a very large order.
If you're a conservative investor or your account isn't large enough, this method can give you a more stable rhythm.

Fixed percentage is different.
What does a fixed percentage mean? Simply put, the amount you invest adjusts based on your overall account situation.
For example, if you set to invest 5% of your account balance, then the larger your account, the more you invest per trade.
The logic is that as you make profits and your account grows, your single trade size also increases, allowing you to better capitalize on good market conditions.
But the obvious problem is that when the market is unfavorable, your losses will also be amplified.

Honestly, there is no absolute optimal choice.
Fixed percentage can indeed allow your gains to grow dynamically during good market conditions, especially when you profit several times in a row, and your account grows rapidly.
But this also means the risk increases; during a downturn, losses can be larger.
The stability of fixed amount is stronger, and your psychological pressure is lower, but in a bull market, it might feel a bit conservative.

My suggestion is to ask yourself a few questions first:
How much fluctuation can you accept?
Are you aiming for steady accumulation or trying to amplify gains by seizing opportunities?
What is the current size of your account?
Choose based on these factors.
Sometimes, you can try both methods to see which one suits your current trading style and mindset better.