Yes, you can post 9x16 on Twitter! The platform allows for a variety of image sizes, including vertical images like 9x16. In fact, vertical images can be particularly effective on Twitter, as they take up more space in users' feeds and can be more eye-catching. However, it's important to keep in mind that Twitter does have specific size recommendations for images. For optimal viewing, Twitter recommends a minimum size of 600 x 335 pixels and a maximum size of 4096 x 4096 pixels. Additionally, it's important to consider the content of your image and ensure that it aligns with your brand and messaging. With these considerations in mind, posting 9x16 images on Twitter can be a great way to engage your audience and share your message in a visually compelling way.