system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - Why does USB transfer rate fluctuate?

Why does the transfer rate fluctuate when I'm moving a file from a flash drive to my computer, instead of staying at a constant rate?
gpt
it could be one of two things

1) you are using a mechanical hard drive and it has to spin and search for different free sectors to save the files to.

2) you are copying alot of folders of different sizes. the copy progress bar is based on what file you are currently copying and how many files you have total. if you have 3000 files, 2999 of them are 1 MB and 1 is 1 TB, it will base the progress as a percentage of 3000 files until it finds the huge 1 TB file. then it will start to take that into consideration.