Notepad++ insists "dependancy" is the correct spelling, while Google Chrome insists it's "dependency". Who's right?

Solution 1:

Dependant entered English directly from the French in the 1590s, with the nominal form dependancy attested from ca. 1610. Compare the word pendant. Dependancy meaning a territory subordinate to another state dates from 1680. The Latinate forms dependent, dependency commonly used today gradually supplanted the French borrowing by ca. 1800. American newspapers, however, were still using dependancy in the colonial sense at the beginning of the twentieth century.

So why should a computer program think that dependancy is a current spelling? Most likely because it was coded in India:

Proudly Made in India! ... They have been able to reduce their dependancy on scheduling different machines ( often from different contractors).

Farming in India - Benefits of organic farming for small farmers include high premium, low investment, less dependancy on money lenders, traditional knowledge, and synergy with life forms.

Headline: Monsoon is a dependancy India can never wean off from

Is insulin a dependancy drug?

The Pharmaceuticals Export Promotion Council of India (Pharmexcil), under the ministry of commerce and industry, is working on a zero dependant manufacturing mechanism in order to reduce the dependancy on imports.

In the rest of the Anglosphere, these spellings would be quite uncommon, but not in India.