Currently, the most common disease is the new coronavirus disease identified as COVID-19. Various techniques to identifying the COVID-19 disease have been offered. Computer vision techniques are widely used to classify COVID-19 with the use of chest X-ray images. Rapid clinical results may prevent COVID-19 from spreading and help doctors treat patients under high workload conditions. As the normal diagnosis phase of illness with a laboratory test is time-consuming and requires a well-equipped laboratory, the X-ray imaging technique is a fast and cheap diagnostic tool for COVID-19. Machine learning methods can enhance the diagnosis of COVID-19 as a decision support platform for radiologists. This chapter utilizes various convolutional neural network (CNN) models, including pretrained models, to classify X-ray images into three classes: COVID-19, pneumonia, and normal. CNN, a form of deep neural networks that have become dominant in various computer vision tasks, attracts interest across various domains, including radiology. Pretrained models on ImageNet are good at detecting high-level features such as edges and patterns. These models understand certain representations of features, which can be reused. Also, deep classifiers have shown promising results in many kinds of work across various domains. We drew some useful results from these classifiers, which could be used faster when detecting COVID-19. Experimental results showed that the accuracy of the VGG19 classifier is 97.56%.