nit colleges are based on crl rank or ews rank

See each college have some Reserved seats. So NIT's have both Unreserved seats as well as Reserved seats. Now the selection is done in a manner which I am describing below. Suppose for example, a NIT have 100 seats among which 10 seats are for EWS and 30 seats for other castes and 60 seats for UR category. So on the basis of CRL this 60 seats will be filled. The 10 seats will filled on the basis of your EWS rank.

This is an analogy and i hope you understood.

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I hope this answer helps. All the very best for your future endeavors!