Why this matters
The Registration Act, 1908 sets out which documents must be registered. Wills are not in that compulsory category; they may be registered if the maker chooses. Validity comes from the Indian Succession Act, 1925 instead — writing, signature, and attestation by two witnesses.
So registration is an evidentiary step, not a validity step. It records that a document in those terms was presented on that date, which can be useful where relatives may later produce a competing version.
What NRIs should consider
Registration happens in India
It is done at a sub-registrar's office. NRIs generally register during a visit, or decide it is not worth a trip since validity does not depend on it.
It does not fix a badly executed will
If the signing and witnessing were wrong, registration will not save the document.
It is not probate
Probate is a court process after death that confirms the will and the executor's authority. Whether it is needed depends on the assets, the institution and local rules.
Execution and storage matter more
Sign correctly with two neutral witnesses and keep the original somewhere your executor can physically reach.
When professional legal advice may be appropriate
Consider speaking with a lawyer qualified in India if your estate spans several countries in a complicated way, if significant tax planning is involved, if a family dispute or contested estate is likely, if a business, trust or unusual ownership structure is part of the estate, or if you are unsure how a Will made where you live interacts with one covering Indian assets.