How soon after arriving in France must I validate my student long-stay visa?

A long-stay visa marked VLS-TS only becomes a valid residence permit once you complete the online validation step after you land in France. This must be done within the first 3 months of arrival through the official ANEF online portal, and a validation fee applies.

Missing this deadline can leave you without legal residence status even though you hold a visa. Validate it early, keep the confirmation, and do not wait until close to the deadline, because problems with the online process can take time to resolve.