Am I allowed to bring a shampoo bottle onto a plane or no?

In 4 days I'm going back to Florida, going on Jetblue. I'm bringing a backpack and a luggage but I'm gonna check in my luggage so I'm just carrying my bag.
Am I allowed to put like a 8 inch shampoo bottle into my backpack (I'm gonna wear my backpack inside the airport).

No. Put it into your checked luggage.

Pretty much disallowed. People try to carry that sort of thing, but the machine picks it up as liquid and they tell you to go back to baggage check-in and check in your backpack with the shampoo, moisturizer, or whatever else it is. Of course if you don't want to check your backpack, you have to lose the shampoo. If you need the shampoo once you arrive and claim your luggage, you can put it into the luggage. But don't try to take it through the security machine.

The bottle is no problem. As long as it's empty.

If there's shampoo in it, it won't be allowed.

Why were you unable to look this up? Troll?

You can't bring a bottle that big in your carry-on luggage, unless it's empty. The size limit for containers of liquid in carry-on luggage is 3.4 ounces. Even a bigger container only partly full is not allowed.

Just put it in your luggage and you will be fine.

You can put it in your checked luggage, but the bottle can't come onto the plane with you (unless it's demonstrably empty)

Shampoo is considered a liquid/gel. All liquid/gel items must be in containers that are 3.4oz/100ml or smaller. You can take as many of those containers as you can fit into a single 1qt clear Ziploc baggie. You will have to take that baggie out of your bag at security.

Any larger liquid/gel items will have to be packed in a checked bag (which goes in the cargo hold). There are no size and number restrictions on liquids there.