Two sides of the market. Every service here connects job-seekers with employers, or prepares one for the other. Who pays depends on the service:

How campus hiring works. In India, companies visit colleges to hire final-year students, through the college's placement cell. They set an online test first, then hold interviews. Online platforms now let companies reach students at many more colleges than they could visit.
Competitions and internships. Companies run coding contests, hackathons and case competitions for students. These help them find good candidates. They also make the company known among students, which the industry calls employer branding. Internships, including remote ones, give students work experience before their first job.
Going abroad. India is one of the largest sources of international students in the world. Students going abroad need an English test, admission to a university, and money: a scholarship or an education loan. Study-abroad companies help with all of these. They usually earn commissions from the universities that enrol their students, and from the lenders whose loans the students take.

Employers' own hiring software is covered elsewhere.
Every company named here has posted software engineering jobs in India. Famous companies that don't actively hire software engineers in India are left out.
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One company here serves working doctors instead
Four more companies work in this area:
Graduates used to be hired into entry-level jobs such as writing simple code, testing and customer support. That is the work AI models do first. The services here are shifting from finding a first job to preparing for a different one. For India's millions of graduates, the open question is what that first job will become.
Who these companies hire, and for what, is on What edtech companies hire for.