NEW YORK (AP) – Sale ending soon! Only two left! This is a hot item! If you’ve shopped online, you’ve probably seen those messages. What you may not realize: They’re designed to make you spend more.

Online stores have adopted tricks used for years by infomercials and home shopping networks. The only difference now: online stores are trying to get you to click the buy button.

After reviewing 200 of the top shopping sites, including Amazon, eBay and Macys.com, a study by the University of Michigan’s School of Information found that all the sites had an average of 19 features that could encourage impulse buying, such as limited-time discounts and wording that made an item seem like it was almost out of stock.

The best way to combat them? Being aware of the tactics retailers use.

“The onus is on the consumer,” says Paco Underhill, author of “Why We Buy: The Science of Shopping.”

Here’s what to watch out for:

ALMOST SOLD OUT 

Be suspicious of messages that say an item is almost sold out. They’re easy to fall for, since more people are shopping on their phones and have less time to shop, says Underhill, who is also the founder of retail consulting firm Envirosell.

He says shoppers should take a break and check back a couple of hours later, especially if it’s an item you don’t really need. Chances are the item is not really selling out and you may decide you don’t want to buy it after all.

FALLING PRICES 

On Amazon, it’s common for the online shopping giant to show a crossed off “list price” and a lower price it is selling the item for. Don’t rely on that, says Edgar Dworsky, a consumer advocate who runs ConsumerWorld.org. He recommends searching for the item on other sites to see if there’s an even lower price.

Another tip: use price tracking site CamelCamelCamel.com, which can show you how the price has changed over time and let you know if it has been cheaper.