Please help us help you and fill where relevant:
Your LimeSurvey version: 5.6.0+
Own server or LimeSurvey hosting: own server, using cPanel and Softaculous
Survey theme/template:
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I noticed the directory tmp/assets contains thousands of subdirectories, and is taking more than 3 GB now.
May I safely delete it? 
May I control its size?
I've barely used LimeSurvey in the last couple years, there is no survey running, but the assets dir keeps growing.
 

ggenellina wrote:

I've barely used LimeSurvey in the last couple years, there is no survey running, but the assets dir keeps growing.
 

What do you mean by keeps growing? If you currently don't create or modify surveys, I would not expect to see new directories in the assets directory.
How many surveys are still in your LimeSurvey system?

You can delete the stuff inside. You can refresh the assets via the button "Clear assets cache" via Global settings -> General.

 

There were about ~2500 subdirectories in tmp/assets, 3.2 Gb in size.
I have two surveys created, none of which has been active for a year or more.