How this industry works
Every other page here answers “which tool”. These answer the questions that decide whether the answer is usable at all — what an exchange charges for its own prices, who owns the identifier on a security, what an index licence covers. Reference pages, corrected in place rather than dated, each one cited.
How a stock-tip group chat makes money from your order
Why free WhatsApp stock-tip groups and investment clubs profit from members' buy orders, what the FBI, FINRA and the SEC describe, and what to check first.
Next to FundamentalsUpdated
What a stock-alert service's track record proves
Why a US or UK stock-alert or picks service's published record is usually arithmetic on prices, not fills, and what to ask for before you pay for one.
Next to JournalsUpdated
What CME futures data costs a retail trader, and who counts as one
CME bills each of its four exchanges per device, on top of your platform. The rates, the non-professional test, the bundle, and what automation changes.
Next to Trading PlatformsUpdated
What replaced the $25,000 pattern day trader rule
FINRA replaced the PDT rule with intraday margin from 4 June 2026, but firms may phase in until 20 October 2027, and cash accounts were never under it.
Next to Trading PlatformsUpdated
When trading software has to register as an adviser
Why auto-trading and backtesting vendors say they are not a CTA or an investment adviser, which exclusions they rely on, and what that leaves the buyer with.
Next to No-Code TradingUpdated
Why a stock's float differs from one screener to the next
Float is shares outstanding minus holders someone judged not for sale. Which holders, as of which date, is a rulebook choice that moves percent of float short.
Next to Charting & ScreenersUpdated
Why ADR dividends arrive smaller than the declared amount
The depositary bank converts the dividend and takes its fee before your broker sees it. Where the per-ADS fee is written, and how to price it before buying.
Next to DividendsUpdated
Why an ETF's cost differs between the issuer page, prospectus and KID
Gross or net of a waiver, with or without other funds' fees, with or without trading costs. Each cost document answers a different question about one fund.
Next to ETFsUpdated
Why your cost basis breaks after a merger
After a merger the issuer publishes the basis effect on Form 8937, your broker must apply it to covered shares, and a tracker usually has no feed of it.
Next to TrackersUpdated
Why real-time SPX, VIX and Russell values cost extra
An index value is the index owner's product, not an exchange feed. Its fee sits outside the SEC-filed schedules, so every platform passes on a different price.
Next to Charting & ScreenersUpdated
Why an AM-settled SPX option settles at a number not on the chart
Third-Friday SPX options and VIX derivatives settle on a special opening quotation built from opening trades, a number that can fall outside the day's range.
Next to OptionsUpdated
Why US ETFs are not sold to retail investors in Europe
The block is a document, not the fund. The EU's PRIIPs KID, the UK's move to product summaries, and the PFIC rules that mirror it for US persons abroad.
Next to ETFsUpdated
Why an ETF's price, NAV and holdings differ between sources
Three numbers on three clocks. NAV once a day, a price all day, holdings daily from the issuer or quarterly from the SEC — and why two holdings files disagree.
Next to ETFsUpdated
How to read Rule 605 and Rule 606 execution and routing reports
What US execution-quality (Rule 605) and order-routing (Rule 606) reports contain, who must publish them, where the files are, and what they cannot show.
Next to Trading PlatformsUpdated
Short interest, short volume, fails and borrow fees: four clocks
Who reports each US short-side number, under which rule, on what clock, and what each one leaves out. Why the four never reconcile, and what 2028 changes.
Next to Insider & 13FUpdated
Why a stock's beta differs from site to site
One stock, several betas. Window, return frequency, benchmark index, currency, Blume adjustment and leverage, and what each source says it uses.
Next to FundamentalsUpdated
Why consensus estimates differ from site to site
One company, several consensus EPS figures. Who collects the estimates, which analysts count, GAAP or adjusted, fiscal year, currency, and how a beat is scored.
Next to FundamentalsUpdated
How aggregators reach your brokerage account
Password, OAuth token or broker API key — how SnapTrade- and Plaid-style aggregators read a brokerage account, and why the US open banking rule does not help.
Next to Account APIsUpdated
Financial MCP servers, and the licence behind them
MCP changes how market data reaches a model, not who may send it. The mechanism from the spec, three exchanges' published AI positions, and what breaks.
Next to MCP ServersUpdated
What 23-hour stock trading changes in your market data
The US consolidated tape is scheduled to run 23 hours a day from 6 December 2026. What moves in trade dates, daily bars, volume, flags and calendars.
Next to Trading PlatformsUpdated
Why real-time stock data is so expensive
You are not paying the API vendor, you are paying the exchange — and in US markets the exchange's price list is filed with the SEC and public.
Next to Market DataUpdated
When a trade shows up in the public record
Form 4, Schedule 13D, 13F and congressional reports each run on their own clock. What each contains, how old it is when you see it, and what it never shows.
Next to Insider & 13FUpdated
Why dividend yield differs from site to site
One dividend, several yields. Forward or trailing, which dates, special payouts, SEC yield for funds, which price and currency — and what each source uses.
Next to DividendsUpdated
Why implied volatility and Greeks differ between platforms
Same option, same moment, two IVs and two deltas. The model, the quote, the clock, the rate and the dividend each platform chose, and how to find which.
Next to OptionsUpdated
Why options data costs more than stock data
OPRA's per-user fee is close to the stock tape's. The cost is two million series, a 40-gigabit feed, a licence that reaches delayed data, and the model.
Next to OptionsUpdated
Why two charts show a different daily candle for the same stock
Same stock, same day, two candles. Which feed, which trades, which close and which day boundary each chart used, and how to find the one that differs.
Next to Charting & ScreenersUpdated
Can you train a model on licensed market data?
Training is not a word most data licences use. How exchange policies and vendor terms map it onto non-display use, derived data and redistribution.
Next to BacktestingUpdated
Choosing a database for tick data
A day of US equity quotes is 1.9 billion records. Why row stores fail on it, why the as-of join decides the engine, and how to size before you pick.
Next to Tick StorageUpdated
What a charting library licence allows
Apache-2.0 with a link, free under contract, per-seat or watermarked — what financial charting licences permit, and why none of them covers the prices you draw.
Next to Charting LibrariesUpdated
Why two libraries give different RSI, EMA and ATR values
RSI, EMA and ATR are recursive, so the seed, the smoothing constant, price adjustment and bar boundaries all change the number. Where libraries differ.
Next to Analysis LibrariesUpdated
Why two retirement calculators give different success rates
Same savings, same spending, two success rates. Replayed history or Monte Carlo, which return and inflation series, fees, timing, and what counts as success.
Next to RetirementUpdated
Why your portfolio tracker and your broker show different returns
Same account, two percentages. Return formula, dividend dates, exchange-rate fixings, fees and cost-basis method, and how to find which one moved the number.
Next to TrackersUpdated
Why two stock screeners return different lists for the same screen
Same filter, two lists. Where a screener's universe, trailing-twelve-month figures, share counts and sectors come from, and why tools build them differently.
Next to Charting & ScreenersUpdated
What alternative data actually costs
Satellite counts and card panels are sold by contract, not by price page. What the industry spends, why nobody quotes a number, and what a small buyer gets.
Next to Market DataUpdated
CUSIP vs ISIN vs FIGI: which identifier to build on
Tickers are free and ambiguous. CUSIP, ISIN and SEDOL are unambiguous and licensed. FIGI, LEI and CIK are unambiguous and free — start there.
Next to Market DataUpdated
Free stock market data, and where the free layer stops
The genuinely free financial data is published by regulators and central banks, not vendors. What that covers, and the first thing you have to pay for.
Next to Market DataUpdated
Historical S&P 500 constituents and survivorship bias
An index's historical membership list is licensed data, not a public fact. What point-in-time constituents cost, and the free route that works going forward.
Next to BacktestingUpdated
Where research terminals get their data
Koyfin, TIKR, GuruFocus and Stock Rover all publish who supplies their numbers. What those wholesale licences are, and what they stop a product doing.
Next to FundamentalsUpdated
Who owns the market data industry
The visible brands are terminals. The durable positions sit underneath — exchange data rights, identifiers, index licensing, ratings — mapped from filings.
Next to Market DataUpdated
Why two providers give different returns for the same stock
Adjusted close is computed, not observed. How splits, dividends and spin-offs are folded back through history, and why two correct series disagree.
Next to Market DataUpdated