Short answer
Market replay plays back past sessions candle by candle, so you can practise many trading days in a short time whenever you want. Paper trading uses live prices in real time with simulated money. Replay is better for building a large sample quickly; paper trading is better for real-time patience. Most traders benefit from both.
Definitions
Market replay
Historical data is hidden past a chosen point and revealed at a speed you control. You trade the session as if it were live, but you can do it at night, at weekends, or five times in one afternoon.
Paper trading
A simulated account connected to live market data. Orders are simulated, but the session happens in real time, so you have to be at the screen when the market moves.
Side-by-side comparison
| Factor | Market replay | Paper trading |
|---|---|---|
| Speed | Skip quiet periods, several sessions per day | One live session at real speed |
| Sample size | Builds a large trade sample quickly | Builds slowly, day by day |
| Realism | Real historical prices; you know it's the past | Live prices; fills may be optimistic |
| Emotional pressure | Lower | Somewhat higher, still no real money |
| Scheduling | Any time, including weekends | Only during market hours |
| Market conditions | Pick specific days (news, trends, chop) | Whatever the market gives you today |
| Cost | Free tiers exist; deeper history may be paid | Often free with a broker or platform, sometimes needs data fees |
When replay is useful
- — You want 50 trades of practice on one setup this month, not next year.
- — You can't be at the screen during your target session.
- — You want to study specific conditions, such as CPI or FOMC days.
- — You're backtesting a manual strategy and need consistent rules across many days.
When paper trading is useful
- — You need to practise waiting, since you can't fast-forward.
- — You want to rehearse your exact live routine: alarms, prep, broker screen.
- — You're close to trading live and want a final check in current conditions.
Using both together
A practical split: use replay to develop and test a setup across many sessions, then paper trade that same setup live for a few weeks. If your live-sim behaviour matches your replay behaviour, you've learned something real. If it doesn't, the gap tells you what to work on, usually patience or overtrading.
Watch for hindsight bias in replay. Choose sessions without looking at the daily chart first, and don't replay the same day until you have forgotten it.