The default provider is Yahoo for new stocks. However, a different provider can be defined for each different stocks with the Stocks Panel. Google, Quandl have each their advantages, like currencies for Quandl. Also, local providers like kbd_Japan for Japan, India_NSE for India, and trading_ASX for Australia are focused on a few local exchanges.

Note, to enter a stock with a provider different from Yahoo, you have to
add the code and the name manually.

Intraday data are downloaded from
Google

You also have the ability to use Paid Providers to access extra data. At this point, EODData (Platinum account) offers access to commodities, futures and foreign exchanges markets in the US, UK and Canada.

An automatic update is launched when the application opens, looking for any available quotes data, unless you uncheck the box in the preferences panel.


Yahoo: Yahoo has the largest stock coverage. The search field, in the stock panel.

http://finance.yahoo.com/exchanges


Google: Google only covers US, UK, China (inc. Hong Kong) for historical data, but it is the provider for most of the intraday data.

http://www.google.com/intl/en/googlefinance/disclaimer/


Quand: Quandl is an open collaborative effort with millions of data sets from hundreds of sources. You have to do a bit of research but it’s worth it. For example, code for Apple is GOOG/NASDAQ_AAPL, code for Gold is OFDP/GOLD_2, etc... Note Quandl covers many other things beyond stocks like real estate data, crime trends, or even UFO sightings (NUFORC/SIGHTINGS).
Important: Registration is free BUT you have to register before using them. Once registered, go to your account profile, API tab. You’ll see a 20 characters authentification token. Enter that token in Mastock, Preferences, Internet page.

http://www.quandl.com/markets/global-markets-overview

http://www.quandl.com/sources


GoogleQuandl: Designed as a limited alternative to both Quandl and Google, it accepts either Google or Quandl codes. The reasons this provider was developed are:
  • Google enables long term historical data only for the US, UK, China and Hong Kong markets. This provider extends coverage to all Google codes, all markets.
  • Quandl is sometimes slightly late updating their own Google data
The key limitations however are, (a) only 200 days are downloaded, enough for most indicators and (b) it depends on Google good will not to change key construction of their download web pages. If issue, just select all stocks with this provider, and switch to Quandl all at once.


EODData: You need a Platinum account to use them and, as of 2013, it’s 29.99USD/month. They cover many exchanges, including Futures, Commodities and Currencies. Once you have your account, go to Mastock, Preferences, Internet and enter your user name and password.
To add an
EODData code, you then have to use the Third-Parties Screen

http://www.eoddata.com/default.aspx


Trading_ASX: Covers only the Australian market.
http://www.tradingroom.com.au/apps/index.ac


KBD_Japan: Covers several japanese stock markets.
http://k-db.com/site/default.aspx

India_NSE: Covers the Indian NSE exchange. Data directly extracted from NSE.
http://www.nseindia.com