Real saffron strands have a deep red color with a slight orange at the tips. Avoid saffron that looks too bright yellow or pale.
Authentic saffron has a strong aroma that is sweet, earthy, and floral whereas fake saffron may have a sweet fragrance with a faint chemical smell
Real saffron is a little bitter with a slight sweet taste. If it lacks bitterness or is too sweet, it may be fake.
Real saffron threads tend to remain intact when rubbed between fingers whereas fake ones will fall apart.
Mix saffron and baking soda in a container, then pour water in the container, the water should turn yellow, if not, it isn’t real saffron.
Add a few strands of saffron to warm water, it may take 15 minutes to an hour to release yellow color in water, but if it loses its color within minutes and water turns red or releases no color at all then it is most probably fake.
Saffron is one of the most high-end spices and it is pretty expensive so if it comes cheap then it's most likely not genuine at all.