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In computing, a scanner is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in many offices today are variations of the desktop (or flatbed) scanner where the document is placed on a glass window for scanning. Hand-held scanners, where the device is moved by hand, were briefly popular but are now less common due to the difficulty of obtaining a high-quality image. Perfunctorily driven scanners that move the document are normally used for large-format documents, where a flatbed design would be unrealistic.

Currently available scanners typically use charge-coupled device (CCD) or Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image antenna. A rotary scanner, used for high-speed document scanning, is another type of drum scanner, using a CCD collection instead of a photomultiplier. Other types of scanners are planetary scanners, which take photographs of books and documents, and 3D scanners, for producing three-dimensional models of objects.

Another type of scanner is digital camera scanners, which are based on the notion of reprographic cameras. Due to increasing decision and new features such as anti-shake, digital cameras have become an attractive alternative to regular scanners. While still containing disadvantages compared to customary scanners, digital cameras offer unmatched advantages in speed and portability.