Level 2 order book practice, running in your browser
A live Level 2 book, running in your browser. Watch the depth build on one side and drain from the other — that asymmetry is the whole skill.
What the two columns are
Best bid and offer · resting size · the spread between them
The bids column is the buy side — prices buyers have posted, best at the top. The asks column is the sell side — prices sellers have posted, best at the top. The top line of each is the one that matters: the best bid and the best offer. The gap between them is the spread, printed under the two columns, and it is what you give up the moment you cross instead of waiting. The figure beside each price is the size resting there, and the shading behind it is that size measured against the largest resting order on either side, so you can see at a glance where the book is thick and where it is paper.
Depth is not a promise
Depth is the size sitting at each price, and it tells you roughly what it would take to push the price one level. A thick level absorbs; a thin one gaps. What it does not tell you is intent — resting orders can be pulled in the time it takes to click, and a wall that looks solid from a distance can be gone on approach. The demo above redraws the whole ladder about once a second, or once and then not again if your system asks for reduced motion. Either way the lesson is the same: the picture you are reading is already out of date.
What the tape adds
Every line under time and sales is a trade that has already happened, tagged with the side that crossed to get it done. A taker buy lifted the best offer; a taker sell hit the best bid. The book shows what people say they are willing to do, the tape shows what they actually did, and the two disagreeing — a heavy stack of bids while every print keeps landing on the bid — is worth more than either read on its own.
The demo just lets the book move. Scenario drills — iceberg orders, spoofing, thinning liquidity into the close — plus scoring and difficulty levels are in Order Book Trainer.