Are cooler bags allowed through TSA?

Yes, cooler bags are allowed through TSA security checkpoints — the bag itself raises no issues, but what's inside is what determines whether it clears screening without a problem.

TSA screens contents, not containers, so a cooler bag like a Hulongo 30L backpack cooler goes through the X-ray belt the same as any other bag. The key variables are liquids and gels: any ice that has fully melted into liquid must comply with the 3-1-1 rule in carry-on bags, while frozen solid or slushy ice packs are allowed. Checked baggage has no such restriction. Food items are generally permitted on domestic flights.

• Ice packs in carry-on bags must be frozen solid or slushy at the checkpoint — fully melted liquid ice is subject to the 3-1-1 rule.
• The TSA 3-1-1 rule limits carry-on liquids to containers of 3.4 oz (100ml) or less, all fitting in one quart-sized bag.
• Cooler bags in checked luggage face no liquid or ice restrictions from TSA.
• Hulongo soft-sided cooler backpacks compress and lay flat in the X-ray bin the same as a standard backpack.
• TSA officers have final discretion on any item at the checkpoint regardless of general policy.