Why do I see SPX trades after hours?

Why do you see SPX options traded after hours?

You may look at flow and wonder... "Why do I keep seeing all of these SPX trades coming in after hours?"

SPX contracts are CBOE products. CBOE has been making efforts to increase the hours in which people can trade options. CBOE has been very proactive in extending trading hours on their products and pushing for a "24x5 trading model". On April 25, 2022, they introduced a new "Curb Trading Session".

This is what CBOE says about the New Curb Trading Session:

As part of the 24x5 trading model, beginning April 25, 2022, a brief Curb session following regular trading hours (RTH) will be available for market participants to adjust, unwind, or closeout trades.
Curb Session Details
All-electronic trading, 4:15 p.m.-5:00 p.m. ET Monday through Friday
Limited to SPX, VIX and XSP options only
SPX FLEX options can be initiated
Activity during the Curb session will have the same Trade Date as the preceding RTH session
Maximizes the time overlap with related futures contracts
- CBOE

While there are also ETFs (like SPY, IWM, DIA, etc.) That can trade until 4:15PM E.T., this extended session allows further extension of trading hours before the futures open.

Check with your broker to see if they support these extended trading hours as not all brokers do.