How to Become a Registered Market Maker
How to become a market maker: exchange registration, two sided quoting size and width rules, net capital under Rule 15c3-1, and what suspension means.
Liquidity & spreads
Bid-ask spreads, depth, and what it really costs to trade, with liquidity measured on the actual tape, from megacaps to microcaps.
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Why Market Makers Lose Money: Adverse Selection
Why do market makers lose money? Adverse selection is the main channel. See how markout curves measure it, plus inventory risk and queue position costs.
Quote-Driven vs Order-Driven Markets
Quote-driven vs order-driven markets, defined plainly, plus the hybrid reality of US equity trading and what depth each structure actually shows you.
How ETF Creation and Redemption Works
ETF creation and redemption is the primary market retail never sees. How authorized participants swap baskets for shares, and why that loop pins price to NAV.
Why Your Options Order Isn't Getting Filled
Why your options order isn't filling: exchange priority rules, pro-rata allocation, resting size that reprices, and net-price routing for spreads.
Can You Trade US Stocks 24 Hours a Day?
Can you trade US stocks 24 hours a day? Almost. The four windows explained, with data on which hours the tape prints and how wide spreads get overnight.
What Is Average Daily Volume (ADV)?
Average daily volume is a stock's typical shares traded per day. It is the denominator inside days to cover, relative volume, and every liquidity screen.
What It Costs to Trade a Stock, Measured
Commissions are zero, but every stock trade pays the bid-ask spread. See the real cost of trading stocks, measured in basis points across 12 household names.
What Is the NBBO? National Best Bid and Offer
The NBBO is the national best bid and offer, the one consolidated stock quote your broker must match or beat. See how fast it updates, from real tick data.
Locked and Crossed Markets, Explained With Data
A locked market quotes the bid equal to the ask; a crossed market quotes the bid above it. See why Reg NMS bans both and how often each hits the tape.
Why Are Spreads Wider at the Open? Real Data
Why are spreads wider at the open? Tick-level quotes price the opening premium half hour by half hour, show how fast it fades, and what premarket really costs.
What Is Dark Pool Trading? FINRA Volume Data
Dark pool trading matches stock orders with no displayed quotes. Every fill prints to the FINRA tape, the measured off-exchange share of five liquid stocks.
What Is a Block Trade? Big Prints & the Data
What a block trade is, where the 10,000-share / $200,000 rule comes from, and how big prints reach the tape, dark pools, exchanges, on real block-trade data.
What Is RVOL (Relative Volume)? How to Read It
RVOL (relative volume) is a stock's volume ÷ its 20-day average: above 1 is busier-than-usual trading. Plus intraday time-of-day RVOL and what counts as high.
Premarket and After-Hours Trading Hours (ET)
Premarket runs 4-9:30 a.m. ET, after-hours 4-8 p.m. See what the tape shows: each session's volume share, how much wider spreads cost, and when news moves.
What Is the Closing Auction? (Closing Cross)
What the closing auction is, why one 4 p.m. print sets the official close, and how market-on-close orders feed the day's biggest trade, on real tape data.
What Is a Bid-Ask Spread? Real Costs
Learn what a bid-ask spread is, how to calculate it, and what it costs per trade, with real spreads measured from tick-level quote data on US stocks.
How Do Market Makers Make Money? The Spread
What market makers do and how they earn the bid-ask spread, with real tick data: measured spreads, quote updates per second, and the SQL behind every number.