Are ETFs shortable stocks?

Hi,

I read a past thread saying that SPY and QQQQ are not shortable under Interactive Brokers. However, I have checked their shortable lists and both SPYs and QQQQs are there. I have also checked that USO is there but when I check the "availability", it is "3,000". How I am supposed to know that I can short, say, USO given the availability amount? Are all 3 of them shortable?

Really appreciate if someone could clears things up.

 

All 3 (spy, qqqq, uso) show "green" in my TWS, i.e. they are shortable.

 

What column do you add to TWS to see "green" or I suppose "red"?

What if after you are short, the color change to red shortly after, or the next day, do you then have to cover?????

 

Ultras are shortable also (SSO, QLD)...can be beneficial based on price versus the inverse.

 

These largest of etf's are not always shortable. I tried shorting the q a few days ago and I got the box that said they would have to locate shares.