How long is the student visa duration for masters in the US for a Master's?

The F-1 student visa for a US master's program is valid for the length of your course, plus a short grace period. The visa’s expiration date is the last day you can enter the US, but your authorized stay depends on your Form I-20 and maintaining full-time enrollment.

After graduation, you may be eligible for up to 12 months of work authorization through Optional Practical Training (OPT), with possible extensions for STEM (science, technology, engineering, math) fields.