The way out is not the way in

An order book has two sides and people picture them as mirrors. They are not. The money standing behind a buy and the money standing behind a sell are different amounts, on the same venue, in the same second, and the gap is often large enough to decide whether a position was worth taking.

Getting in and getting out are different prices

Position sizing is almost always done on the entry. You check what it costs to get in, the number looks acceptable, and you take the trade. The exit is assumed to be the same trade backwards. On several of the books here the two sides differ by more than half their own size, which means a position that was cheap to open can be materially dearer to close, and nothing about the entry told you so.

And it is not a property of the venue

The same venue can be lopsided in one market and almost perfectly balanced in the next one, at the same moment. So this is not a fact you can learn once about a place and carry with you. It is a measurement that has to be taken for the market you are actually in, at the time you are actually in it.

Why nobody publishes this

A spread is symmetric by construction, so quoting it lets a venue describe its market with one number that is true for buyers and sellers alike. The moment you separate the sides you are publishing a figure that is worse for half your customers, and which half changes through the day. There is no version of that number a venue wants on its own marketing page.

What this page will not claim

These feeds return the top of each book rather than all of it, so every figure here is bounded by what is visible, and an order larger than that is reported as unknown rather than given a flattering number.

Live books load in a moment. If you are reading this, they have not arrived yet.