<h1>8 Hours.</h1>
The elf trance is often misunderstood as being that the long rest is only 4 hours whereas everyone else is 8 hours. 
The only thing the elf trance does is you need to sleep "trance" for 4 hours, but still need the remaining 4 hours to gain the benefit of a long rest such as other light activity.

The benefit is such that the elves can keep watch for longer (up to 4 hours). Whereas most other humanoids need 6 hours of sleep and 2 hours of light activity (or 8 hours of sleep if you like sleep ofc). 

**TLDR**:
8 Hours - 4 hour trance + 4 hour light activity/downtime.
Just for reference that elves do in fact need 8 hours for a long rest: 
https://www.sageadvice.eu/elf-trance-does-it-affect-long-rest-for-elves/