A PSD is a Photoshop design file. Technically, it stands for Photoshop Document, which is a proprietary file type from Adobe. Adobe’s Photoshop is the software most widely used for web design and works best for the design-to-code process.PSD files are typically opened and edited with Adobe Photoshop, but can be opened with Adobe Photoshop Elements, and even certain non-Adobe products such as Corel’s PaintShop Pro and GIMP. However, programs other than Photoshop will not be able to fully edit or even read the complex layers utilized in many PSD files. Other advanced features within a PSD design may not be properly recognized, either.