Who Are the Biggest Market Makers?
Who are the biggest market makers? The firms that quote US stocks and options, and how to read your own broker's Rule 606 report to see who fills your orders.
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Evergreen explainers of how US markets actually work, each concept taught with real, queryable market data.
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.
Mini Index Options Explained: XSP, XND, MRUT
Mini index options let smaller accounts trade S&P 500 and Nasdaq 100 exposure at a fraction of the size. XSP, NANOS, XND and MRUT, plus the liquidity catch.
How ADRs Work: Ratios, Fees and Dividends
How ADRs work, from the ratio that sets the US price to the depositary custody fee taken out of your dividend, with the payout data behind each step.
Dividend Reinvestment Plans (DRIPs) Explained
How a dividend reinvestment plan works: the three kinds of DRIP, why you buy at the pay date price, and the tax lot each reinvestment quietly creates.
Good Faith Violations in Cash Accounts
A good faith violation happens when you buy with unsettled proceeds and sell before they settle. Here is the T+1 rule, worked examples, and the 90 day penalty.
Historical Volatility vs Implied Volatility
Historical volatility measures what a stock already did; implied volatility is the market's forward guess. See both computed, side by side, with real data.
How Preferred Stock Dividends Work
Preferred stock dividends are a stated rate on par value, with rules common shares never carry. Cumulative terms, arrears, stoppers and call risk, explained.
Early Lockup Release: Triggers and Waivers
Early lockup release explained: the price conditions in IPO underwriting agreements, and the discretionary waivers underwriters can grant without one.
International Fund NAV: Fair Value Pricing
Your international fund's holdings stopped trading hours before its 4 p.m. NAV. See how fair value pricing adjusts those stale closes, with the data.
Event Contract Arbitrage: YES + NO vs $1
One YES plus one NO always pays $1 at settlement. Here is how event contract arbitrage works when the two books disagree, and what fees and collateral cost.
ETN vs ETF: the credit risk you own
ETN vs ETF: one owns assets, the other is unsecured bank debt. See what happened to holders when issuers failed or called the notes, with the data.
How Futures Margin Works: SPAN and Calls
How futures margin works: initial versus maintenance levels, SPAN scenario risk, the nightly variation margin cash move, and why intraday rates vanish.
Non-Marginable Securities: Reg T vs House
Non-marginable securities carry a 100% cash requirement. Here is where that comes from, how Reg T and house rules differ, and how to check a current one.
Due Bills and Stock Splits: Ex-Date Timing
Why a stock split's ex-date lands after the payable date, what a due bill is, who tracks it, and the full timeline from record date to first adjusted session.
MOC and MOO Order Cutoff Times: NYSE & Nasdaq
MOC and MOO order cutoff times on NYSE and Nasdaq, plus the later deadline after which an on-close order can no longer be cancelled or reduced in size.
The Vendor Display Rule: SEC Rule 603(c)
The vendor display rule in plain English: what SEC Rule 603(c) makes you show alongside a quote, and why the line between display and internal use is argued.
Market Cap and Which Share Count It Uses
Market cap is price times a share count, but which one? Shares outstanding versus the weighted average count and float, and how to spot a stale vendor number.
Cost Basis Methods: FIFO vs Specific ID
Cost basis methods decide which shares you sell first: FIFO, LIFO, HIFO, and specific ID. See how each one changes the realized gain on the same sale.
Schedule 13D vs 13G: Rules and Deadlines
Schedule 13D vs 13G explained: who must file at 5% beneficial ownership, the shortened 2023 deadlines, and why a 13G to 13D switch matters far more.
How Event Contracts Settle: Payout and Fees
How event contracts settle: the dollar payout, full collateral, who resolves the outcome, and how a one cent fee shifts your breakeven at 90 cents.
Midpoint Peg Orders Explained: Half-Cent Fills
A midpoint peg order floats at the middle of the national best bid and offer. See how half-cent price improvement works and when it is worth almost nothing.
How to Read a Futures Symbol (ESZ6, CLF27)
Read any futures symbol on sight: root, month code, year digit. Worked examples for ESZ6, CLF27 and ZCK6, the full month table, and two traps to avoid.
What Real-Time Market Data Actually Costs
What does real-time market data cost? The three layers of a live data bill, the exchange fees behind it, and why delayed and historical feeds stay cheap.
When Is SQ Day for Nikkei 225 Options?
SQ day is the Nikkei 225 settlement price built from Friday morning opening prints. Here is when it lands each month and what happens to an open position.
Pin Risk at Options Expiration Explained
Pin risk at options expiration: what happens when a stock closes right on your short strike, and why the option holder decides your Monday position.
What Is Form N-PORT? Fund Holdings Filing
What is Form N-PORT? The monthly SEC portfolio report that lists a fund's full holdings, derivatives, borrowings and liquidity buckets, line by line.
When Did the US Stock Market Start? 1792
The US stock market started with the 1792 Buttonwood Agreement, signed by 24 brokers. Every date that follows, and how a call auction became 9:30 to 4:00.
Stop Order vs Stop-Limit Order: How Each Fills
A stop order becomes a market order and fills at any price. A stop-limit becomes a limit order and can miss the exit entirely. Five years of gap data show it.
How to Read a Form 4 Insider Trading Filing
How to read a Form 4 insider filing, from the Section 16 filer rules to what each transaction code means, with data from a full year of SEC filings.
Professional vs Non-Professional Market Data
Professional vs non-professional market data status decides your exchange fees. The occupational tests, self-certification, audits, and why OPRA differs.
Fully Paid Securities Lending Explained
Fully paid securities lending, explained: how a broker lends your shares to short sellers, who posts collateral, and why a dividend arrives as cash in lieu.
Dividends vs Buybacks: Shareholder Yield
Dividends vs buybacks, measured the same way: how to compute buyback yield, total shareholder yield, the 1% excise tax, and why share count settles it.
Qualified Dividend Holding Period: 61 Days
The qualified dividend holding period is more than 60 days inside a 121-day window around the ex-dividend date. See the exact count, with worked dates.
Straddle vs Strangle: Break-Evens and Margin
Straddle vs strangle, compared on the four things most guides skip: break-even math, margin on the short side, probability of profit, and expected move.
SEC 30-Day Yield vs Distribution Yield
SEC 30-day yield vs distribution yield: what each number measures, and why the same fund can advertise two very different figures on the same day.
Portfolio Dividend Yield: Weighted Average
How to calculate portfolio dividend yield: total annual income divided by market value, plus why averaging the yield column misleads and what fixes it.
Poor Man's Covered Call: How the Trade Works
A poor man's covered call swaps 100 shares for a deep in the money LEAPS call. See the capital math and the coverage rule that most guides leave out.
Can You Sell on the Ex-Dividend Date?
Can you sell on the ex-dividend date and keep the dividend? Yes, if you owned the shares at the open. Here is the record date and settlement chain behind it.
Best Time of Day to Sell a Mutual Fund
Is there a best time of day to sell a mutual fund? Forward pricing says no, and the exceptions, broker cutoffs and fair value pricing, are where money leaks.
Time in Force Explained: Day, GTC, IOC, FOK
What is time in force? Day, GTC, IOC and FOK decide how long your order stays live and what counts as a fill, plus the auction cutoffs that end it.
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.
What Is Option Rho? The Interest Rate Greek
Option rho measures how interest rate changes move option prices. See why it is nearly invisible on a 30 day call and material on a two year LEAPS.
Iron Condor vs Iron Butterfly: Break-Evens
Iron condor vs iron butterfly: the same four legs, one strike moved. Both break-evens worked out, plus the vega and fill costs each structure carries.
Credit Spread vs Debit Spread: Same Trade?
Credit spread vs debit spread: on the same strikes both verticals pay the same. See the payoff grid, the parity math, and the three things that really differ.
How to Roll an Option Position: Up and Out
How to roll an option position: close the near contract, open a further one. See what the net credit hides in your break-even and your assignment risk.
Level 1 vs Level 2 vs Level 3 Market Data
Level 1 vs Level 2 vs Level 3 market data, explained with real quote panels: top of book, depth by price, order by order, and what retail feeds skip.
Anchored VWAP Explained: Formula and Uses
Anchored VWAP starts its running average at a bar you choose and never resets. See the formula in plain Python, and what moving the anchor does to the answer.
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.
The Sub-Penny Rule and Price Improvement
Rule 612, the sub-penny rule, bans quotes in fractions of a cent above $1.00. Here is why your fill still printed at four decimals, with real tape data.
Is a Dividend Safe? Free Cash Flow Test
Is a dividend safe? Learn the free cash flow coverage test: operating cash flow minus capex versus dividends paid, plus the filing checks that catch trouble.
Japanese IPO Lockups: The 1.5x Release Rule
Japanese IPO lockups often release on a price condition, commonly 1.5x the offer price, as well as a fixed date. Both triggers explained, with the filings.
Why Stocks Halt: Limit Up-Limit Down Bands
Why do stocks halt? Limit up-limit down bands pause trading for five minutes when price runs past a rolling reference. Here is the machinery, with data.
What Is a Calendar Spread in Options?
A calendar spread sells the near dated option and buys the longer dated one at the same strike. See the term structure and greeks data that sits behind it.
SpaceX Lockup Expiration Date: How to Find It
How to establish the SpaceX lockup expiration date for SPCX from the primary filings, and what the standard 180 day convention actually counts from.
Return of Capital in ETF Distributions
Return of capital is the gap between a covered call ETF's headline distribution rate and its dividend yield. Here is what each part does to your cost basis.
Payment in Lieu of Dividends, Explained
A payment in lieu of dividends arrives when your broker lends your shares out. Here is the full mechanic, and why the tax character differs from a dividend.
Options Expiration Calendar 2026: All 12 Dates
The full 2026 options expiration calendar: twelve monthly third Fridays, the four quarterly dates, and the holiday rule that can shift one to a Thursday.
Margin for Selling Naked Options: Reg T Math
How much margin does selling a naked option take? The Reg T minimum formula, both branches, worked in a short Python script and on real option chains.
IV Rank vs IV Percentile: Formulas Explained
IV rank vs IV percentile: both formulas, one worked example you can check by hand, and the case where the two numbers disagree sharply on the same ticker.
How to Read an Options Symbol (OSI Format)
How to read an options symbol: decode the OSI root, expiry, call or put flag and eight-digit strike, plus adjusted roots, SPXW and why 00007500 is $7.50.
How Stock Settlement Works Under T+1
How stock settlement works under T+1: trade date versus settlement date, what clearing does in between, and why ex-dividend and record date now match.
FINRA Margin Debt Statistics, Explained
FINRA margin debt statistics explained: the rule behind the filing, the third week release, the four to seven week lag, and how to read the history since 1997.
When Are 13F Filings Due? 2026 Deadlines
13F filings are due 45 days after each quarter ends. The four 2026 deadlines, the rolls that move them, and what the form never shows you about a portfolio.
What H1 and H2 Mean in Company Reporting
H1 and H2 are the two halves of a reporting year. What the labels mean, how to read FY26 Q3, and why H1 2026 covers different calendar months by issuer.
Why Stock Quotes Are Delayed 15 Minutes
Why are stock quotes delayed 15 minutes? How exchange data licensing sets the rule, and what a quarter hour of staleness actually costs on real prices.
How the Put/Call Ratio Is Calculated
How the put/call ratio is calculated: the volume and open interest formulas, why index readings run higher, and what counts as a normal reading in 2026.
Portfolio Delta and Beta Weighting Explained
Raw option deltas do not add up across tickers. Beta weighting rescales portfolio delta into equivalent SPY shares, worked through a small book by hand.
$10,000 in a Mutual Fund for 5 Years: The Math
What does $10,000 in a mutual fund become in 5 years? The compounding math at six return rates, plus what a 0.05% and a 1.00% fee each cost in dollars.
How Mutual Fund NAV Is Calculated: Example
How is mutual fund NAV calculated? The formula, the 4 p.m. ET strike, forward pricing, accrued expenses, and a full worked example you can reproduce yourself.
Iceberg Orders Explained: Hidden Liquidity
What is an iceberg order? How the displayed slice and hidden reserve work, why each refresh loses queue priority, and what the pattern looks like on the tape.
ETF Premium and Discount to NAV, Explained
An ETF premium or discount to NAV measures the pricing mechanism more than the portfolio. Here is how the gap forms, and the checks that catch a false alarm.
What Is the Sharpe Ratio? Formula and Math
The Sharpe ratio is average excess return divided by the standard deviation of excess returns. Get the formula right, then see where the number misleads.
Stock Dividend vs Cash Dividend, Explained
A stock dividend adds shares and cuts the price to match. A cash dividend moves money out of the company. See what each does to yield and to cost basis.
How to Calculate Covered Call Returns
How to calculate covered call returns: net debit, break even, static return and return if called, worked through one contract, plus the annualized catch.
Put-Call Parity Explained, With Real Numbers
Put-call parity is the fixed link between a call, a put, the stock, and cash. Worked on a real option chain, plus the implied dividend and borrow rate.
What Time Do Options Stop Trading?
What time do options stop trading? Most stop at 4:00 p.m. ET, while broad index options keep printing until 4:15. See the exact last print, minute by minute.
When Does a Stock Split Take Effect?
A stock split takes effect on the ex-distribution date, usually the business day after the payable date. Here is the full timeline, with due bills explained.
REIT Payout Ratio: FFO vs EPS Explained
A REIT payout ratio above 100% of earnings is normal. See how FFO and AFFO measure dividend affordability, and which warning signs actually matter.
Dividend Withholding Tax for Non-US Investors
Dividend withholding tax takes a cut at source, before US payouts reach a foreign account. See the 30% rate and what a valid W-8BEN treaty claim changes.
What Is Maximum Drawdown? Depth vs Recovery
Maximum drawdown is the largest peak to trough fall in a value series. See what counts as a deep one, and why the climb back to a new high takes longer.
How Implied Volatility Is Calculated
Implied volatility has no closed form solution. See how a solver backs it out of an option price by iteration, the Python that does it, and the traps.
What Is the High-Low Index? Market Breadth
The High-Low Index is the 10-day average of Record High Percent. See the formula worked in round numbers, plus the sample size trap on a quiet tape.
When Is the COT Report Released?
The CFTC releases the COT report every Friday at 3:30 pm ET, measured as of Tuesday's close. See the schedule, the three-day lag, and how to read it.
US Market Hours and Daylight Saving Time
US market hours never change in New York: 9:30 to 16:00 ET all year. See what daylight saving does to the open in London, Frankfurt, Tokyo and Sydney.
How Stock Splits Affect Your Options
A stock split adjusts your options automatically. See what happens to the strike price and the 100 share deliverable, and where the math gets strange.
What Happens If an Option Expires In the Money
If an option expires in the money by at least $0.01, the OCC exercises it automatically. See what the long and short sides owe, and what pin risk costs.
How to Find a Stock's Earnings Date
A company sets its own earnings date and confirms it in a press release and an 8-K filing. Here is where to look, and how far an estimated date can move.
Price Return vs Total Return: The Real Gap
Price return vs total return: the S&P 500 headline index leaves out dividends. See the compounding gap measured over 20 years and where each version is used.
Can an AI Trading Track Record Be Verified?
What would make a public AI trading track record verifiable? The six receipts a reader can demand, and why one live quarter of results proves nothing.
Circuit Breakers for Trading Bots
Circuit breakers stop a trading bot before a bad session compounds. See how often a daily loss limit trips and what volatility scaling does to position size.
When Do Mutual Funds Pay Dividends?
Mutual funds pay dividends monthly, quarterly or annually, and hand out capital gains once in December. See the calendar, the NAV drop and the tax trap.
Event Contract Prices as Probabilities
An event contract settles at $1 or $0, so its price is a probability. See why Yes plus No costs more than $1, and how to strip the spread back out.
How to Find a Lockup Expiration Date
A lockup expiration date lives in the IPO prospectus, not on a calendar page. Where to find it, and why counting 180 days from the first trade gets it wrong.
Nikkei 225 Options and SQ Settlement
Nikkei 225 options settle in cash against the SQ, an opening print from all 225 stocks. How the second Friday settlement works and what long premium costs.
DAX Daily Options: How Eurex 0DTE Works
DAX daily options expire every trading day on Eurex. See how European exercise, the 17:30 CET cash settlement and euro pricing differ from SPX 0DTE.
Highest Dividend Yield US Stocks in 2026
The highest dividend yield US stocks are mostly prices that fell. See the screen, the payout ratios beside each yield, and how often the payout gets cut.
Trailing vs Forward Dividend Yield Explained
Trailing dividend yield counts the last twelve months of payouts; forward yield annualizes the latest declared one. See why two screeners can disagree.
Learn Quant Trading From an Open Source Book
An open source quant trading book lays out the whole syllabus. See what each stage teaches, where most beginners stop, and which parts transfer to US stocks.
Mutual Funds vs ETFs: What Actually Differs
Mutual funds vs ETFs: one price a day at NAV against a live market price. See what really differs in pricing, spreads, capital gains, and share classes.
S&P 500 Dividend Yield: How It's Measured
The S&P 500 dividend yield is cap weighted dividends over total market value, not an average of member yields. See the arithmetic and eleven years of readings.
How to Calculate Dividend Yield: 3 Ways
Dividend yield is annual dividends per share divided by price. Work the formula on Coca-Cola, see trailing vs forward vs yield on cost, and when it misleads.
SCHD vs VOO: Why the Dividend Yields Differ
SCHD screens for dividends, VOO holds the whole S&P 500. See how far apart their yields sit, what the screen selects, and how the SEC yield differs.
Pattern Day Trader Rule: What Replaced It
FINRA retired the pattern day trader rule on June 4, 2026. See what the intraday margin level framework allows now, and what your broker may still enforce.
How Risky Is Options Trading? The Mechanics
How risky is options trading? Risk depends on the structure: a long call caps loss at the debit paid, a naked short call has no upper bound. See the data.
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.
Selling Mutual Funds at a Loss: How Basis Works
Selling mutual funds at a loss: what cost basis really includes after years of reinvested distributions, and how the wash sale rule can disallow part of it.
When Do Mutual Fund Trades Settle?
Mutual fund settlement runs on a different clock than fund pricing. Walk a sale through both clocks, day by day, and see when the cash is really yours.
Dividend Payout Ratio: How to Calculate It
The dividend payout ratio is dividends divided by earnings. See both formulas, what counts as normal by sector, and why cash flow tells a steadier story.
What Is a Good Dividend Yield in 2026?
There is no single good dividend yield. See where US payers actually cluster, and how sector norms and the 10-year Treasury reset the bar for income.
What $1,000 a Month in Dividends Takes
$1,000 a month in dividends is one division: $12,000 divided by yield. See the capital each yield level asks for, and what reaching for an 8% yield costs.
Paper Trading Before Real Money
Paper trading proves your order mechanics and leaves psychology untested. See what simulator fills omit, how long to practice, and which metrics matter.
What Is Max Pain in Options? The Real Math
Max pain is the strike where option holders collect the least at expiry. See the calculation on a real SPY chain and how close settlement actually landed.
Trading US 0DTE Options From Japan
Trading US 0DTE options from Japan puts the opening bell at 22:30 JST. See the session on the Japanese clock, hourly volume, spreads and access mechanics.
Monthly Dividend Stocks Explained
Monthly dividend stocks pay twelve times a year. See why quarterly is the US standard, which structures pay monthly, and how the two yields compare.
Is High Implied Volatility Good? IV in Context
High implied volatility is not good or bad by itself. See what an 80 percent IV reading means against the market, a stock's own range, and realized moves.
How to Read an Option Chain, Column by Column
An option chain lists every strike and expiration for one stock. See what the bid, ask, volume, implied volatility and delta columns each measure.
The 8-4-3 Rule for Mutual Funds, Explained
The 8-4-3 rule says a monthly fund plan hits one milestone in 8 years, doubles it in 4 more and triples it in 3. See the arithmetic and what the data shows.
What Is the VIX? What It Really Measures
The VIX is a 30 day implied volatility reading priced from S&P 500 options. See what a level of 15 or 30 means in daily move terms, and what VIX products cost.
0DTE Options Strategies: How They Trade
0DTE options strategies explained: credit spreads, iron condors and lottery calls, the gamma clock that governs them, and what the options tape shows.
What Is the Efficient Market Hypothesis?
The efficient market hypothesis says prices already carry known information. See its three forms, and the weak form measured on five years of US stock data.
Covered Call vs Cash-Secured Put
A covered call and a cash-secured put at one strike share a payoff shape. See both priced on the same SPY chain, and where the two really differ.
The 3-5-7 Rule in Options, Examined
The 3-5-7 rule caps risk at 3% per trade, 5% per underlying and 7% of the account. Where the folk rule came from, and how it holds up against the data.
US Stock Market Hours Around the World
US stock market hours run 9:30 a.m. to 4:00 p.m. New York time. See that session converted into major world time zones, plus the twice yearly clock shifts.
Covered Call vs Collar: Income or a Floor
Covered call vs collar: the added put turns income into a floor. Both positions traced through one real SPY window in June 2026, valued side by side.
The Wheel Strategy: How the Loop Works
The wheel strategy sells a cash-secured put, takes assignment, then sells covered calls. We trace both legs through one real pair of SPY option contracts.
American vs European Options Explained
American options can be exercised on any trading day, European options only at expiration. How SPY and SPX differ, and when early exercise matters.
Free Stock Market Data API, No Key Required
A free stock market data API with no key and no signup: seven curated JSON queries over US equities and options, cached at the edge and open to AI agents.
Free SQL API for Stock Market Data
A free SQL API for stock market data: write real SQL against 22 years of US equities, dividends, and fundamentals. 100 queries a day, no credit card.
What Is Volatility Skew? The Smile, Measured
Volatility skew is why downside puts cost more than upside calls. We measured it on SPY strike by strike, then across every US option chain at once.
What Is IV Crush? Measured on Real Earnings
IV crush is the overnight collapse of option implied volatility after an event. We scanned six weeks of the US options tape and measured every big one.
Which Stocks Have Daily Options?
SPY, QQQ and IWM list a new options expiration every trading day, and the index roots go deeper. See which tickers carry dailies and which only get Fridays.
When Is Short Interest Released?
FINRA publishes short interest twice a month, mid-month and month-end, about two weeks after each settlement date. See the live release cadence and lag.
The Low-Volatility Anomaly
The low-volatility anomaly says more risk does not reliably pay. We line up two years of realized volatility against the return each large-cap stock delivered.
How Often Do Stocks Split?
How often do stocks split? A data study since 2016: reverse splits far outnumber the forward ones that grab headlines, hundreds of each every year.
Highest Days to Cover Stocks Right Now
The stocks with the highest days to cover from the latest FINRA short interest settlement, and why the raw top of the list is a liquidity artifact.
Triple Witching 2026 Dates and Volume Data
Triple witching 2026 falls on March 20, June 18, September 18 and December 18. See how market-wide dollar volume moved on the last witching session.
How Ex-Dividend Dates Affect Options
How ex-dividend dates affect options: why ordinary dividends don't move strikes, when to exercise a call early, and how a liquid option's greeks glide through.
Does a Stock Go Up After a Split?
Does a stock go up after a stock split? A data study of forward splits since 2016: the run-up comes before, and the median stock trailed the market afterward.
What Is a Special Dividend? (With Examples)
A special dividend is a one-time payout outside a company's regular schedule. Why Costco and National Beverage pay them, and what they mean for options.
How Leveraged ETFs Work (and Why They Decay)
How 3x leveraged ETFs like SOXL actually work, why they can beat or lag their multiple over time, and why inverse funds such as SOXS keep reverse-splitting.
The Option Greeks Explained: Delta to Rho
Delta, gamma, theta, vega and rho, the five option greeks, demonstrated by tracing one real SPY call through its whole life against the stock.
What Is Implied Volatility? IV, Explained
Implied volatility is the future move an option's price implies. See IV across stocks, the term structure, the volatility skew, and a year of SPY's vol regime.
What Is Option Vega? Volatility Sensitivity
Vega measures an option's sensitivity to implied volatility. Watch IV spike on a real SPY call, see vega grow with time, and drive the earnings vol crush.
What Is Option Theta? Time Decay Explained
Theta measures an option's daily time decay. Watch it deepen on a real SPY call into expiry, see decay accelerate, and why it's the seller's income.
What Is Option Gamma? Delta's Accelerator
Gamma measures how fast an option's delta changes. See the at-the-money bell, why it spikes near expiry, and how it powers 0DTE and the gamma squeeze.
What Is Option Delta? A Plain-English Guide
Option delta measures how much an option moves per $1 in the stock. Watch it track a real SPY call across the strike and see the moneyness S-curve.
Most Shorted Stocks Right Now, Measured
The most shorted stocks by days to cover and by shares short, from the latest exchange-reported settlement. Liquid names only, refreshed as new prints land.
Is the Stock Market Open Today?
Is the US stock market open today? A computed open/closed status, today's calendar, every upcoming holiday, and what happens to orders placed while it's closed.
Unusual Volume Stocks This Week, Measured
Unusual volume stocks this week, ranked: trailing-week turnover vs. each name's prior 40 sessions, with weekly returns, rarity context and persistence.
When Do Mutual Funds Trade? NAV Pricing at 4 pm
Mutual funds trade once a day, priced at the 4 pm ET NAV, no intraday prices, no limit orders. See when orders fill, the broker cutoff, and T+1 settlement.
When Do 0DTE Options Trade? By the Hour
0DTE options trade heaviest in the morning, not at the close: hourly volume, the calls-vs-puts clock, weekday shares and same-day spreads, all measured.
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.
IPO Lockup Expiration: Meaning & Release Date
A lockup expiry is the day IPO insiders can finally sell, customarily 180 days after listing. Where to find the exact end date, and how five unlocks traded.
FINRA Short Interest Data, Explained
Where short interest data actually comes from: FINRA's twice-monthly settlement file and its daily short volume file. Schedules, contents, and failure modes.
What Is the Put-Call Ratio? A Data Guide
The put-call ratio is puts traded divided by calls traded. See its real range on the full US options tape: by expiration, index vs equity, and against a decade.
DTE Meaning in Options: Days to Expiration
DTE stands for days to expiration: calendar days, not trading days, until an option expires, and expiry day counts as zero. How to count it on a real chain.
Upcoming Ex-Dividend Dates: Stocks This Week
See which stocks have upcoming ex-dividend dates this week and next: the biggest names, per-share payouts and pay dates, plus what the ex-day price drop does.
What Is Triple Witching? Volume & Volatility
Triple witching is the quarterly session when index futures, index options and stock options expire together. Volume and volatility, measured on the real tape.
When Do Options Expire? Friday 4 PM ET & Daily
Most options stop trading at the 4:00 PM ET close on expiration Friday; weeklies expire Fridays, monthlies the third Friday, and SPY and QQQ expire daily.
What Is Dividend Yield? What's Normal in 2026
Dividend yield is annual dividends per share divided by price. See the median payer's yield, what's normal by sector, and when a high yield is a trap.
What Is a Short Squeeze? GameStop, Measured
A short squeeze is a rally that feeds on short sellers buying to close. GameStop's 2021 records, short interest, days to cover and price, tell it in numbers.
Why Do Stocks Gap Up or Down Overnight?
A gap up or gap down is the distance from the prior close to the 9:30 open, after 17.5 closed hours. SPY overnight gap size, Mondays widest, plus stop risk.
What Is Days to Cover? Short Interest Ratio
Days to cover, the short interest ratio, is shares short divided by daily volume: how many days the exit would take. Real settlement data shows what is high.
What Is a Stock Split? Ratios and Mechanics
A stock split multiplies share count and divides price, value unchanged. Real split records show which ratios companies pick, and what prices did next.
Market Order vs Limit Order, Measured
A market order fills now at the best available price; a limit order caps your price but may not fill. Real quote data shows what each choice costs in dollars.
How Monthly Stock Returns Are Measured
A monthly stock return depends on which two prices you pick, whether dividends count, and whether the series is split-adjusted. Each one measured on real data.
How Much Does It Cost to Trade Options?
Options commissions may be zero, but the bid-ask spread is real. See the median cost to trade SPY, QQQ, IWM, GLD, and TSLA options, in basis points.
What Is 0DTE? Zero Days to Expiry Options
0DTE options expire the same day they trade, zero days to expiry. What DTE means, how traders build a 0DTE trade, and one real contract traced to the bell.
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 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.
What Is FINRA Short Interest? Days to Cover
FINRA short interest is shares sold short and not yet bought back. See how it's reported twice monthly, settlement dates, days to cover and percent of float.
What Is a Reverse Stock Split? Good or Bad?
A 1-for-10 reverse stock split turns 10 shares into 1 at ten times the price, position value unchanged. Neutral arithmetic; the companies that use it are not.
Stock Market Hours: Open 9:30, Close 4:00 ET
What time does the stock market open and close? NYSE and Nasdaq regular hours run 9:30 a.m.–4 p.m. ET, plus premarket and after-hours; closed weekends.
Ex-Dividend Date vs. Record Date: Same Day?
Is the ex-dividend date the same as the record date? Since the T+1 switch in May 2024, yes, they fall on the same day for nearly every US dividend, measured.
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.
How Big Is the OPRA Options Quote Feed?
How big is the options quote feed? We count one full day of OPRA-scale NBBO updates in our warehouse and measure it against the entire stock quote tape.
What Is the Opening Auction? How Stocks Open
What the opening auction is, how one 9:30 a.m. cross sets each stock's official opening price, and why the open can differ from the first trade of the day.
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.
Stock Float vs. Shares Outstanding Explained
A stock's float is the shares free to trade, shares outstanding minus locked-up insider stock. See what counts as a low float and how thin floats trade.
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.
Options Volume vs. Open Interest, Explained
Volume counts contracts traded today; open interest counts contracts still outstanding. Both defined, plus one full day of the US options tape, measured.
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.
The Most Common SEC Filings, Explained by Data
The most common SEC filing is not the 10-K or the 10-Q. It is the insider Form 4. A data-backed guide to EDGAR's busiest forms, ranked, defined and explained.
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 VWAP? Volume-Weighted Average Price
VWAP stands for volume-weighted average price. Definition: price times volume divided by total volume, reset daily. What it means on a real trading day.
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.
Stock Market Holidays 2026–2027: NYSE & Nasdaq
When is the stock market closed? Every upcoming NYSE & Nasdaq holiday and 1:00 p.m. early close for 2026–2027, from the live exchange calendar.
Why Short Interest Data Is Always Two Weeks Old
Short interest is measured twice a month and published on a lag. The FINRA cycle, the measured delay, what moves while a print is pending, and days to cover.
What Is the 2s10s Spread? Yield Curve Data
What the 2s10s spread is, how the Treasury yield curve works, and what past inversions looked like, with every chart built from auditable market 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.
Short Interest vs Short Volume: The Difference
Short interest and daily short volume measure different things. See real per-ticker numbers, days-to-cover math, and the exact query behind every figure.
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.
What Is an Ex-Dividend Date? How It Works
The ex-dividend date decides who gets paid: buy before it and the dividend is yours, buy on it and it isn't. See the four key dates on real US timelines.