Mewing is a facial reconstructing technique that involves keeping the tongue on the roof of the mouth to change the shape of the jawline. The technique is named after Dr. John Mew, a British orthodontist who promotes a form of orthodontics called "orthotropics" that focuses on "jaw posture" including retraining the position of the tongue. The basic idea behind mewing is that you can change the shape of your jawline if you think about the placement of your tongue in your mouth. The technique involves resting the tongue at the palate, or top of the mouth, rather than at the bottom, with the lips touching and the teeth closed. Over time, the movement is said to help realign the teeth and define the jawline.

While supporters of the technique believe that mewing can change the shape of the jawline and alleviate jaw pain, there is no serious research that suggests mewing can change the shape of the jawline or help with other issues. Experts say its unlikely that one will see any permanent change. Before and after images on social media, TikTok, and YouTube are not reliable sources of evidence, as photos can be doctored, or the angles and lighting can prove more flattering.

To properly mew, one must relax the tongue and make sure its entirely against the roof of the mouth. While the technique is easy to do, it requires a considerable amount of time and patience to see any results. The main risk to mewing is employing this technique as a replacement for a research-based treatment that would have helped more efficiently.