After-hours and pre-market trading: times, risks and data

After-hours trading is the buying and selling of US stocks after the regular session closes at 4:00 p.m. Eastern Time, until 8:00 p.m. ET. Pre-market trading is the same thing before the open, from 4:00 to 9:30 a.m. ET. Together they are called extended-hours trading. Far fewer people are trading, so spreads are wider and a single order can move the price.

This explainer covers the times, why extended-hours prices behave differently, and how those prints appear in a quote feed. For the full schedule in every time zone, with holidays and early closes, start with the guide to stock market hours. For pulling the prices into your own code, see the stock API guide.

Pre-market and after-hours trading times

On the two early-close days of 2026, November 27 and December 24, the regular session ends at 1:00 p.m. ET and after-hours runs from 1:00 to 5:00 p.m. instead of 4:00 to 8:00 p.m. Pre-market hours do not change.

Why extended-hours prices behave differently

During the regular session, market makers, index funds, brokers routing retail orders and every flavour of algorithm meet at once, and the opening and closing auctions concentrate volume into single prices. Outside those hours most of them are gone. What remains is a thinner electronic market in which each order matters more.

• Wider spreadsFewer quotes compete at each price, so the gap between bid and ask opens up and crossing it costs more.
• Big moves on small volumeA few thousand shares can move a price that would absorb a million during the day.
• News lands hereCompanies usually report earnings just after 4:00 p.m. or before 9:30 a.m. ET, so the biggest repricings happen when liquidity is lowest.
• Limit orders, usuallyMany brokers accept only limit orders in extended hours, because a market order could fill far from the last price.

You can watch the effect in real quotes. On Monday, September 28, 2026 at 6:21 a.m. ET, US:KO quoted 88.11 bid and 88.30 ask: a 19-cent spread, about 22 basis points. Shortly before 7:00 a.m. it quoted 88.15 / 88.20, about 6 basis points, as more participants arrived. In the regular session a large, liquid stock like this usually trades a cent or two wide. The bid-ask spread explainer shows how to measure that yourself.

Extended hours do not set the official price

The official open comes from the 9:30 a.m. opening auction and the official close from the 4:00 p.m. closing auction. A stock can rally 5% after hours on earnings and still show yesterday's close as its close until the next session ends. That is why a change figure in pre-market compares the latest trade with the previous official close, not with the last after-hours print.

{
  "symbol": "US:KO",
  "bid": 88.11,5
  "ask": 88.3,
  "bid_size": 400,
  "ask_size": 200,
  "last_price": 88.24,1
  "last_timestamp": 1790589160160,2
  "prev_close": 87.81,3
  "change": 0.43,
  "change_percent": 0.4897,4
  "last_size": 150
}

The same rule shows up in bars. Daily bars carry the official open and close. Intraday bars from GET /stocks/agg cover 9:30 a.m. to the close, so a chart built from them has no pre-market candles and no after-hours spike. That is usually what you want for indicators, and exactly what you do not want for an earnings-night dashboard.

How extended-hours prints show up in market data

To stream extended-hours bars, add session to a stocks.agg subscription. Each frame carries its part of the day, so you can shade pre-market candles or drop them before computing a regular-session indicator. The stock streaming docs list the intervals.

{
  "action": "subscribe",
  "channels": ["stocks.agg"],
  "symbols": ["US:KO"],
  "interval": ["1m", "5m"],
  "session": "extended"
}

Two more details matter in thin hours. First, snapshot-on-subscribe for US stocks replays a last-known quote only if it is recent (about two minutes), so in a sleepy pre-market you can subscribe and hear nothing until the next tick. Call GET /stocks/snapshot/{symbol} first, or subscribe with "snapshot": "always". Second, between 8:00 p.m. and 4:00 a.m. ET the listing markets are closed; the US overnight session add-on covers the most traded US stocks and ETFs on those nights with a derived reference quote aggregated from several sources. Its dispersion_bps field says how far those sources disagree, which is the number to watch on a thin night.

Here is a short script that reports where a stock stands in extended hours and flags that the move is provisional:

import os

import requests

BASE_URL = "https://api.tickerlayer.com"
HEADERS = {"x-api-key": os.environ["TICKERLAYER_API_KEY"]}


def get(path, **params):
    resp = requests.get(BASE_URL + path, params=params, headers=HEADERS, timeout=10)
    resp.raise_for_status()
    return resp.json()


status = get("/markets/status", asset="stocks", market="US")
snap = get("/stocks/snapshot/US:KO")

bid, ask = snap["bid"], snap["ask"]
spread_bps = (ask - bid) / ((ask + bid) / 2) * 10_000

print(f"phase      {status['phase']}")
print(f"last       {snap['last_price']} ({snap['change_percent']:+.2f}% vs close {snap['prev_close']})")
print(f"bid / ask  {bid} / {ask}  spread {spread_bps:.1f} bps")
if status["phase"] in ("pre_market", "post_market"):
    print("extended hours: thin book, treat the move as provisional")

phase      pre_market
last       88.151 (+0.39% vs close 87.81)
bid / ask  88.15 / 88.2  spread 5.7 bps
extended hours: thin book, treat the move as provisional

Reading an after-hours move without fooling yourself