Recently Yahoo Finance discontinued its Free API service to retrive quotes and historical stock market data and the service dead now. It is a big blow for financial market traders/investors who uses Excel, R, MatLab, Python based applications in their studies which fetches from Yahoo Finance API. If you are searching for the alternative then AlphaVantage will surely catch your eyeballs.
Alpha Vantage is a leading provider of free APIs in JSON and CSV formats for realtime and historical stock market data. They also provide API for 50+ technical indicators and chart ready time-series. All you need is to get a free api key from alphavantage.
Alpha Vantage APIs are grouped into three categories:
(1) Time Series Data
(2) Technical Indicators
(3) Sector Performances.
All APIs are realtime: the latest data points are derived from the current trading day. For more details refer the Alphavantage API documentation
Alpha Vantage provides realtime and historical equity data in 4 different temporal resolutions: (1) intraday, (2) daily, (3) weekly, and (4) monthly. Daily, weekly, and monthly time series contain 20 years of historical data. Intraday time series typically span the past 10 to 15 days.
Note: Currently for Indian Markets only realtime quotes are available from Alphavantage. However for US Markets both realtime quotes and Historical time-series data is available currently and moreover data is adjusted to split/bonus and other corporate action.
Currently free API service comes with no daily/weekly/monthly call limits. However for optimal performance alphavantage recommends API call frequency not to exceed far beyond ~200 calls per minute. Data quality is good compared to Google/Yahoo Finance.
Python Library : alpha_vantage ( Python module to get stock data from the Alpha Vantage Api)
PHP Client: Alphavantage PHP Client ( PHP module to get stock data from the Alpha Vantage Api)