I was wondering, How websites such as Yahoo finance and Google can access market data? Do they buy API from somewhere?
closed as off-topic by Nathan L, Dheer, Chris W. Rea, ChrisInEdmonton, JoeTaxpayer♦ Dec 11 '15 at 21:47
- This question does not appear to be about Personal Finance within the scope defined in the help center.
At the bottom of Yahoo! Finance's S & P 500 quote
Quotes are real-time for NASDAQ, NYSE, and NYSE MKT. See also delay times for other exchanges. All information provided "as is" for informational purposes only, not intended for trading purposes or advice. Neither Yahoo! nor any of independent providers is liable for any informational errors, incompleteness, or delays, or for any actions taken in reliance on information contained herein. By accessing the Yahoo! site, you agree not to redistribute the information found therein.
Fundamental company data provided by Capital IQ. Historical chart data and daily updates provided by Commodity Systems, Inc. (CSI). International historical chart data, daily updates, fund summary, fund performance, dividend data and Morningstar Index data provided by Morningstar, Inc. Orderbook quotes are provided by BATS Exchange. US Financials data provided by Edgar Online and all other Financials provided by Capital IQ. International historical chart data, daily updates, fundAnalyst estimates data provided by Thomson Financial Network. All data povided by Thomson Financial Network is based solely upon research information provided by third party analysts. Yahoo! has not reviewed, and in no way endorses the validity of such data. Yahoo! and ThomsonFN shall not be liable for any actions taken in reliance thereon.
Thus, yes there is a DB being accessed that there is likely an agreement between Yahoo! and the providers.
To quote their disclaimer:
Data is provided by financial exchanges and may be delayed as specified by financial exchanges or our data providers. Google does not verify any data and disclaims any obligation to do so.
That means that they buy it from a reseller such as IDC. It probably differs in source between the different exchanges depending on price and availability factors. They do specify in some cases which reseller they use and one of those happens to be Interactive Data (IDC) who are also the data provider used in my day job!