6 Stock APIs to Use in 2021 [Review]

Obtaining reliable stock data can be challenging, especially if you are just starting. Fortunately, finding the best stock API is easy, and we have compiled them in a list. We have checked all of them, based on specific parameters to find the best stock data API and what APIs professional traders are using. You don't need to try all of these APIs again, and you just have to figure out what works best for your needs. There are 6 main data market providers to be reviewed:

1. Twelve Data
2. Polygon.io
3. IEX Cloud
4. Alpha Vantage
5. Intrinio
6. Xignite

Why you need stock API?

Stock data API is the foundation for almost all of the fields related to finance. Starting from trading and up to scientific research projects. Stock APIs save you from the tedious process of obtaining the exchange licenses (that might come at a very high cost!), data cleaning, and ease of access with programming languages.

It gets better when you are a professional user who needs a reliable service to adapt to your increasing requirements. Therefore, we have identified the following 7 criteria to compare against, and they will be used to compound the final score from 0 to 5:

• Data quality
• Real-time data
• Stock global coverage
• Alternative data: forex, crypto, ETFs, indices, etc.
• Streaming data via WebSocket or SSE
• Technical indicators
• Price reasonability

1. Twelve Data 

Overall score: 4.97

The leader of our ranking is the Twelve Data. The data is obtained from the stock exchanges and aggregated into various intervals from 1 minute to 1 month. All the values are obtained in real-time and have a swift response time averaging 170 ms. All US markets are covered (including OTC), as well as others such as Canada, India, UK, Euronext, Germany, Brazil, other European, Latin American, and Asian exchanges. 

This API also covers forex pairs, cryptocurrency, ETFs, funds data, and indices. Stock data, as well as alternative data, can be streamed using WebSocket that are useful for charting applications. An extensive collection of over 100 technical indicators is provided, making it a good suit for comprehensive technical analysis. 

The free tier provides up to 800 requests per day. Unlimited daily access to all data starts from $29.00 if paid monthly and $24.00 if paid annually.

2. Polygon.io

Overall score: 4.65

Having its servers located inside the Equinix data center, the quality and reliability of Polygon's data for US markets are proven to be on the highest level. Data is updated in real-time at very low latency and can be compounded into custom intervals. Unfortunately, Polygon does not cover any international markets apart from the United States. However, some currencies and cryptos are supported in the separate plans.

WebSocket feed can be either streamed delayed or real-time, depending on the subscription plan. There are no technical indicators supported, making it necessary to perform calculations on the client-side. Polygon will be the right choice for those who seek US exchange specific data and is willing to do a lot of additional code.

The first premium package starts at $99 monthly, without yearly billing plans.

3. IEX Cloud

Overall score: 4.58

IEX Cloud is a provider with the most extensive collection of data endpoints ranging from OHLC to SEC filings. The plan pricing calculation fee is obscure at first glance since all of the endpoints have different "weights," and you have to calculate in advance the anticipated usage. Overall the data quality is good, although only the US markets are covered. There is plenty of alternative data, including the forex and the crypto markets. However, it was devasted that no indices are included.

Real-time streaming is supplied via Server Send Events (SSE) as an alternative to WebSocket. Many technical indicators are supported as well as necessary mathematical calculations.

Apart from the starting plan, which is suitable for testing, the next tiers come at the cost of $19, $59, and $699 monthly, depending on the number of allocated messages.

4. Alpha Vantage

Overall score: 4.01

Alpha Vantage used to be one of the first companies that appeared on the market after the Yahoo Finance API shutdown being a decent alternative for the users for a while. At the moment, their data quality seems to be fair, although they stopped providing real-time data for most of the essential stocks, e.g., AAPL. In the documentation, it is not mentioned that international markets are supported. However, if you type in the ticker symbol (perfectly matching Yahoo's format), you should be able to get it. Forex and cryptocurrencies are presented.

At the moment, Alpha Vantage does not support WebSocket, and after contacting their support, they have confirmed that there are no plans to introduce it in the future. Fundamental technical indicators are supported.

The prices begin at $29.99 monthly for 30 API requests per minute.  

5. Intrinio

Overall score: 3.97

Intrinio offers exchange specific data that might differ from the National Best Bid and Offer price (NBBO), which other data providers offer. Data could be accessed in real-time or be 15 min delayed, which comes at a significantly reduced fee. Initially, only the US data is covered. Upon individual request, access to international markets may be facilitated via third-parties. No crypto data is presented. However, it does have forex, fundamentals, and sec fillings.

Several data feeds are streamable via WebSocket, such as TSX Level 1 data. However, it seems to be not the main specialization of Intrinio. A pretty decent collection of technical indicators is presented. 

Fees are calculated based on your use case and can quickly reach a couple of thousands. 

6. Xignite

Overall score: 3.86

This company primarily focuses on enterprise clients. A large number of data is provided directly from stock exchanges. Covers international stock markets, as well as ETFs, mutual funds, and indices. Xignite does not support forex or cryptos. Data could be streamed via SSE. Technical indicators are not presented. 

Prices are available upon request, and after consultation with a Xignite representative, could be in a range from thousands to tens of thousands of dollars.

Conclusion

Stock data providers on that list are curated and checked by industry professionals. They give you insides that otherwise would take months or even years. Your next move would be to choose the provider that does fulfill your usage intent and the budget. Most of the providers have free or trial access. Try them out. See what you need to improve your existing system or build a completely new one. Your success falls on you. Take that next step.