How to Spot Fake Ugg Boots
To spot fake UGG boots, measure how tall the boots are. Real UGG boots will be 11 and three-quarter inches, while fake UGG boots are usually taller. Also, put the boots on and try folding down the opening at the top. If the opening of the boots is too narrow to fold down, they're probably not real UGG boots. If you're still not sure, compare the font on the back of the boots to the font on a real pair of UGG boots. If the font is too big or stylized incorrectly, it's a sign that the boots are fake.
Check the height of your boots. Fake boots are taller than real pairs; you might only be able to tell this if you have a real pair to compare them to, so either hold an old pair next to this new pair, or compare images online. Real boots have a 11 ¾ inch (29.845 cm) shaft height, and fake boots can be up to 2 inches (5.08 cm) taller. The opening of your boots should be wide enough to fold down. If the opening is narrow, your UGG boots are most likely imitations. Check the heel label for the proper font. If the font is large and stylized incorrectly, you will know the boots are knockoffs. The threads on the label of fake UGG boots will be mismatched and asymmetrical. The label on fake boots will be wide and sloppily stitched. Check where the shoes were made. Real UGG boots are made in China, not in Australia, as many fake boots will claim. This should be displayed clearly on the label. Also check for the registered trademark mark (R) on the boots' soles. Observe the box your boots came in. Fake UGGs will come in bulky boxes that are hinged and have handles. They will also use different artwork on their boxes. Real UGG boots will be delivered in a cardboard box with a lid, displaying the sun logo on the front and the company name: “UGG AUSTRALIA” printed on its side. Real UGG boots will come in a thick wrapping paper with “UGG AUSTRALIA” printed on it. Check the label on the box. Real labels display a picture of the product, and the top half of the barcode is colored. Fake labels may state that the boots were made in New Zealand or Australia, and will have a completely black-and-white barcode. Check your boots for a hanging tag. Hanging tags are not used on real UGG products. If you notice a tag, the boots are almost certainly fake. Australian flags displayed on the packaging also indicates that the UGGs are fake. Feel the fur inside the boots. Synthetic fur is slippery, silky, and even feels fake. Real UGG boots use fur that is a bit rougher to the touch. The fur should be a creamy color with a thick texture. Counterfeit boots have grey-colored, thin, synthetic fur on the inside that cannot be seen from the top opening. There is a layer of foam between the inner and outer lining of the boot. Bend the sole of your boot. Real UGG boots are easy to bend and walk in, while fake ones are stiff and unyielding. Gently try to move the sole of your boot to see how flexible it is; if it is difficult to move, the boots may be fake. Look at the security labels. Check the foil strip on the label behind the shoe size and the materials label on the left boot. If there isn't a sewn-in-label, there should be a security sticker on the sole of the left shoe. Turn your boot over to see the holographic UGG label with a sun symbol. If the boots are real, when you turn the boot 90 degrees, it will change from black to white. 
Check the height of your boots. Check the heel label for the proper font. Check where the shoes were made. Observe the box your boots came in. Check the label on the box. Check your boots for a hanging tag. Feel the fur inside the boots. Bend the sole of your boot. Look at the security labels. 