Actually it’s not quite as simple as that, @AnnaProbably .
What you’re saying is obviously true of retail spot forex, and forex CFD’s, but it isn’t true of forex futures, which retail traders also trade.
Those are centralized, on the Chicago Mercantile Exchange or CME, so volume is actually available for them. Among retail traders who become successful, the availability of volume is one of the five or six usual and well-known reasons for people to switch to futures.
Many CFD brokers pretend to be able to give their clients volume figures and charts, but as you already understand, it isn’t market volume.
It’s only the volume of their own customers: obviously they have no other figures to offer. Nobody could. To be very polite indeed about how useful those figures are, let’s just say that they’re of “limited value” and of course that they vary enormously between different brokers.
For two reasons, it’s important for retail forex customers to understand this, as you already do.
Firstly, nobody should be basing their trading decisions around it.
Secondly, nobody should be looking at or relying on any indicators that are volume-based, either. An example would be the Money Flow Index, or MFI, which is a volume-weighted RSI.
If you see forex trading systems, usually on Youtube or in forums, which use indicators like that, you can be pretty sure that their creators have not - unlike yourself! - quite understood what’s going on, and what “volume“ really measures.