On forex and most CFDs, the volume bars you're staring at don't count money. They count ticks — how many times the price was requoted. That's very different from how much was actually traded.
On a centralized exchange — a stock, a futures contract — volume is a hard fact. Every share and contract clears through one venue, so the tape shows exactly how many changed hands. Volume there is a real measurement of participation.
Forex has no central exchange. It's a web of banks, brokers, and liquidity providers, each with its own book. Nobody sees the whole market, so nobody can report true traded volume. What your platform shows instead is tick volume: a count of price updates per candle. If the feed updated 400 times in an hour, the bar prints 400 — whether those updates moved one lot or ten thousand.
Tick volume isn't useless. It correlates loosely with real activity, because busy markets get requoted more often. When London and New York overlap, ticks spike; at the Sunday open, they crawl. As a rough gauge of when the market is awake, it does a job.
But treat it as literal volume and you'll draw false conclusions. A "high volume" breakout on a quiet afternoon might just be a jittery feed in thin liquidity. Two brokers can print different volume on the same pair at the same minute, because they count different feeds. There's no single true number to be right about.
The first-principles takeaway
Volume is one of the three things a market actually gives you — price, volume, time. On forex, know which volume you're holding. Tick volume measures attention, not money. Use it to read rhythm and session structure, not to prove "big players" are behind a candle.