Speed : It is static site generator . It's all static data upload during deployment time of the website . While technology like php , mern had two way talking client & server that make it slow & give bulky experience to user .
Graphql support : By grapql support we able to read fectch the specefic data what we require at given time
Good SEO : In react server to client dymaic change make hard for crawler to do SEO ranking on it . Due to headless cms in gatsby the seo become much easy.
Today most of bloging site convering into jam stack ... because of its static site buid feature
Headless Cms : in jam stack we can use various headless cms like strapi , ghost , netlify cms etc . The benefit of using headless cms is we only require to focus on frontend and the backend part will be managed by headless cms just we require to integriate our project to headless cms api It also made it highly secure as compare to other web app .
Inbuild image optimation : by using gatsby plugin image we can optamise the image . It automatically add responsive images to our website site and also maintain high performance scores can be difficult to do manually. in static folder it had all case of screen avalible on it . Small size of image : it automatically decrease the size of image almost 80% from its original size .
Community support : Jamstack community members have a common mission to promote the web that is free , give high performance , highly secure .