I am adding SEO for Category Page which has more than 1500 products in a category I don't want to put pagination Or any kind of ajax which will load few products and then on page scroll load the next products IS there any way to load all product without letting the user know that page Is loading?
Please be careful, you will have a lot of performance penalties when loading 1500 products on a single request and that will affect your customer's browser (frozen, crashed, etc).
If it's for SEO only I think you can load them at once but using CSS to hide most of them from the view (only show 20-40 products for example). It's still available in HTML code but the client doesn't see them and performance still good.
Whenever they want to see more products, just toggle some CSS classes to show them but using lazy load or pagination to fake the loading.