After-hours trading begins immediately after the 4:00pm ET regular close and runs until 8:00pm at most retail brokers. The first 30-60 minutes capture the post-close earnings releases and are by far the most active. Volumes drop off sharply after 5:30pm and the last hour is typically very thin.
Earnings reactions in after-hours often retrace meaningfully into the following regular open — overnight news flow, sell-side notes and broker-rating changes can all hit between sessions. Traders sometimes use the after-hours print as a price-discovery signal rather than a finished move.
Brokers accept limit orders only in after-hours and may apply tighter trading restrictions on volatile names. Order types that involve a stop trigger are typically not active outside regular hours.
