Companies and ETFs may decide to have a stock split or to declare a large dividend (>10% of the stock price) if the stock price goes up or falls precipitously to encourage more trading interest in the shares.

Options holders get their options shares per contract or strike price adjusted to be similar to pre-split specifications in order to not be positively or negatively affected by the split or large dividend. This is done by the Options Clearing Corporation. There are fields in the Options Price Reporting Authority (OPRA) feed disseminated to brokers and other options front ends to reflect the new shares per contract or strike price for the pre-split options.

Add adjustments for mergers to these split and dividend adjustments, and the treatment of pre-split options gets onerous for options information providers. These splits, dividends and mergers are termed corporate actions.

At ORATS, we handle corporate actions in the simplest way possible that still can be performed in actual trading. For example in backtesting, when the date for the corporate action is known, we simulate exiting the option the day before and re-enter the day after with a new opening scan. In our data, we only show the standard contracts, filtering out non-standard strikes that have a different multiplier than the standard 100 shares per contract. 

VXX is a stock that performs reverse splits. While regular 2 for 1 splits will have a divisor of 2.0, a reverse split of 1 for 4 will have a divisor of 0.25.

Here's how to call our data API to get the splits for a symbol:

Here are trades in VXX. Notice how the split date of 11/9/2010 is avoided: