Revenues, earnings, profit margins, and other fundamental statistics are used to estimate a company's underlying worth and future growth prospects.

The Securities and Exchange Commission offers fundamental data for over 5000 US stocks dating back to 1998. Earnings reports, income statements, and other data fields are among the approximately 900 available statements in their database published daily.

The Securities and Exchange Commission (SEC) of the United States is a large independent federal body established in the aftermath of the 1929 Wall Street Crash. The SEC's major goal is to give the impression that markets are free of market manipulation.

You can manually look into their database and extract individual company financial statements.

Companies publish 10-K forms for annual statements and 10-Q forms for quarterly statements. Each statement has multiple sections. The ones that you want to look at are: the income statement, the balance sheet statement, and the cash flow statement.

Those 3 sections are the crucial elements to understanding a company's financial health.

Let's also look at some Fundamental Data APIs that offer this data already extracted and standardized:

Financial Modeling Prep or FMP

FMP provides great capabilities and covers most of the functions needed for a full fundamental API for developers searching for an easy-to-understand and getable interface to integrate with apps. It pulls data from the SEC and provides standardized statements ready to be pulled from their API and analyzed.

The user interface allows developers to go through each endpoint and choose how they should be used in conjunction with a connected guide plan.

If we're being honest, FMP coverage on a free trial gives you access to many of its features that you won't get anywhere else.

In terms of Stock Fundamentals API they covers most of companies and quant developer needs.

Here are some example of Data they covers:

• 30+ years companies' financial statements
• Insider transactions
• Key metrics and financial ratios for over 10,000 companies

You can also see their process fo parsing financial statements on their parsing financial statements page.

Bloomberg Fundamental Statement API

Professionals who need to make rapid decisions rely on Bloomberg Professional for the most up-to-date stock information, relevant options, and tested stock factors to examine before investing. When working with owners and third-party goals, however, flexibility might be problematic.

From commerce and application supervision to uncertainty and agreement, briefcase management, and analytics, these gadgets are typically loaded with a variety of data sources, raising the likelihood of variances that might obstruct precise calculations.

You can find more about their dataset on their website.

Morningstar Fundamental API

Morningstar has a large range of fundamental APIs. It makes financial statement data, financial ratios, and non public financial data accessible to developers.

Morningstar, like every API, aims to give the current state of a company's assets as well as investment strategies that can provide long-term revenue flow. 

As a result, it is regarded as a basic investing tool that identifies essential financial ratios and allows developers to include pathways to identify company financial health for a long-term investment strategy.

Their complete documentation is available at Morningstar.