The London session is the busiest stretch of the forex day. From roughly 08:00 to 16:00 London time, more currency changes hands through London than through any other centre — the BIS Triennial Survey puts the UK at around 38% of global FX turnover, more than New York and Tokyo combined. If your EA trades EUR or GBP pairs, this is the window where most of its opportunities, and most of its costs, land.
When it runs
The session runs from about 08:00 to 16:00 London time. Because the City works to local hours, that window is fixed in London time and shifts by an hour in GMT terms when the clocks change. It opens while Tokyo is still finishing, giving an Asian-to-London handover early on, and it closes well after New York has opened — which is where the London–New York overlap comes from in the afternoon.
Why volume is highest
London sits in the middle of the trading day, between Asian and American hours, so banks and funds route a large share of their order flow through it. Frankfurt opens an hour earlier, around 07:00 London time, and the two are often grouped together as the European session, which is why flow starts building before London proper is open. Deeper liquidity means tighter spreads on the majors, especially EUR/USD, GBP/USD and EUR/GBP. It also means bigger moves: the London open often sets the day's direction, and the daily range tends to expand once it is underway.
A worked example
Suppose you trade one standard lot of EUR/USD, where each pip is worth about £8. During the quiet late-Asian hours the spread might be 1.4 pips; through the London morning it tightens to 0.5 pips. On a single lot that's the difference between paying about £11 and about £4 to get in and out. Trade ten times a day and the session you trade in decides whether you hand the broker roughly £112 or £40 in spread. Nothing about your strategy changed — only the clock.
The first hour of London (08:00–09:00) carries a chunk of the day's volatility. Spreads are tight, but price can whip, so an EA tuned for calm conditions may behave very differently at 08:05 than at 14:00.
Why it matters for EA traders
Many EAs restrict trading to London hours with a time filter. If that filter runs on the broker's server clock but you read the clock in London time, you can be an hour or two out — trades fire at the wrong moment and your session logic quietly breaks. Costs are also lowest here for the majors, so the execution assumptions baked into a backtest hold up best during London. The afternoon, when New York joins, is the single busiest window of all, and gets its own guide.
The Karnek note
Karnek reads your live terminal, so every trade is timestamped and you can see exactly which session your EA was working in when it opened and closed a position. It shows all of this without any ability to place, change or close a trade — it can only watch.
More in Market Sessions & Timing →
Written and reviewed by the Karnek Research team. Last updated August 2026.
Educational content only - not financial advice. Past performance does not predict future results. Trading carries significant risk.