Freshly popped popcorn can last for up to 3 weeks before it goes stale.
The popcorn will remain safe to eat after the 3 weeks but the popcorn will not be as good tasting and may not be as enjoyable.
Tinned popcorn can last for around 3 months to 4 months before it goes bad and gets stale.
Even then the popcorn is still safe to eat but it's not as fresh.
It's best to eat any popcorn within 3 to 4 weeks of popping it so that it remains fresh.
If you have leftover popped popcorn then you should place it in Ziploc bags to keep it fresh.
As long as you keep the popcorn sealed it will keep for at least 4 weeks before going stale.