Should you opt out of sending SAT scores if they’re not required by a university?

I’m thinking of applying to Depaul University and I saw that they’re test optional, would it be a good idea to not send in my test scores at all?

Depends on how your test scores compare to the average applicant and to the rest of your application. 1500+ SAT - send them. 900 SAT - don’t send them. Pretty hard to provide any advice with zero data.

Or, as they put it
“If you are satisfied with your test scores and believe they are indicative of your academic achievement, then we are happy to consider them as part of your application. If you have a strong academic record demonstrated by above average grades in challenging courses, but do not feel your test results are a good reflection of your academic performance, you can choose not to submit them”

https://irma.depaul.edu/cds/2018/2018CDS_c.pdf section C9 says that 58% of enrolled frosh submitted SAT scores, with a 25th-75th percentile range of 550-650 for the EBRW section, and 530-640 for the math section.