if you prefer a snug fit, have narrow feet, or plan to wear them barefoot.
Individual experiences with "true to size" often vary based on whether users wear socks. buying uggs size guide
Buying UGGs can be tricky because their signature sheepskin lining compresses and "molds" to your feet over time. Most experts and users agree that while they generally fit true to size (TTS), you should aim for a fit right out of the box . Standard Fit by Category if you prefer a snug fit, have narrow
These run true to size but will feel tight initially. Within 10–20 hours of wear, the lining packs down, effectively increasing the space inside by about half a size . if you prefer a snug fit