Classic SharePoint vs Modern SharePoint?

Ans:- Classic SharePoint vs Modern SharePoint

Key Feature	Classic SharePoint	Modern SharePoint
Custom master page and page layouts	Classic SharePoint we able to set custom master page and page layouts by Out of Box SharePoint.	Modern SharePoint does not support any custom master page and page layouts. Modern SharePoint as its own layouts that fully responsive including all modern web parts.
Responsiveness	Classic SharePoint is partially responsive including all classic web part. Classic SharePoint is not mobile friendly.	Modern SharePoint comes with full responsiveness even all modern web parts. Modern SharePoint comes with Team sites, modern list and library structure and site pages. Modern SharePoint support all modern devices including mobiles, tablets and surface devices.
Secure and Faster	In Classic SharePoint user have permission to add custom code (javascript), also have script editor and content editor web part that render on the server side that’s why it takes time to load on the browser with additional security issues. The user can also edit pages in SharePoint designer.	Modern SharePoint doesn’t allow any custom code even it does not provide any script editor web part for custom code that’s why is more secure and loads faster.
List and Library improvements	Classic SharePoint list and library level configuration are most complicated task there is no easy interaction with these controls. Classic SharePoint has ribbon containing all list and library configuration.	Modern SharePoint has many lists and library level improvements including easier filtering, conditional formatting, and attention views, which have easy interaction. The modern list also addressed 5000 list items threshold issues problem by automatically indexing. Modern SharePoint does not have SharePoint ribbon so we miss some cool features that present in classic SharePoint including save as template, export to excel etc.
New feature	Classic SharePoint also supports these modern services but there are some limitation and configuration issues which are not in Modern SharePoint case.	Modern SharePoint comes with very cool features that easy to configure and share data between these services including Flow, Forms, PowerApps, PowerBI etc. with responsiveness.
AlternateCSSUrl web property	Supported	Not supported
Minimal Download Strategy (MDS)	Supported	Not supported
Web part supports	All SPFx web part is supported in Classic pages.	We can’t use already created “classic” web parts on “modern” pages but vice-versa are worked.
Development Strategy	For classic SharePoint Microsoft give feature called SharePoint Add-in in the year 2013 for web part creation. SharePoint add-in requires a lot of infrastructure and efforts to create add-in more it comes in two flavors: SharePoint-hosted and provider-hosted. SharePoint add-in runs in an iframe.	For modern SharePoint pages, Microsoft gives feature called SharePoint Framework (SPFx) in the year 2016 for web part creation. SharePoint framework relly on open source tooling which required fewer efforts. SharePoint framework does not run in an iframe that’s why it capable of running in classic SharePoint site pages also.
Development Customizations	Classic web parts support JSLink for list/form customizations. Supports display templates, master pages offer search result rendering customizations	Modern web parts not supported JSlink in list/form customization. Modern SharePoint development is client side using JavaScript frameworks like Angular JS, React JS, Node etc. all these open sources. SharePoint framework (SPFx) are used to create modern web parts and extensions SPFx extensions can help for Application Customizers, Field Customizers, and Command Sets.
Tools for Development Customizations	SharePoint Designer Infopath SharePoint Workflows Sandbox Solution CustomActions	SharePoint Framework(SPFx)- Web part and Extention PowerApps Microsoft Flow
SharePoint Search	The ”classic” search experience can be found in SharePoint on-prem as well as in Office 365. ”Search Center” provides results from the search index. Full control on the searchable strategy, define what results to be displayed with complete search customization	”Modern” search experiences have been popping up in Office 365 only. Displaying relevant content, moreover, suggesting what is supposed to be useful to the current user but the modern search experience UI is not customizable.
SharePoint Ribbon	Present	Not present

Limitation of Modern SharePoint:

• 1.      Modern SharePoint has come for Office 365 online only. not for on premises.
• 2.     For SharePoint Framework (SPFx) to build and deploy client-side web part so you need Office 365 tenant admin permission to create an app catalog site.
• 3.     No support for master pages and page layouts.
• 4.     No active SharePoint ribbon in modern SharePoint.
• 5.     Custom CSS via AlternateCSSUrl web property not supported
• 6.     Minimal Download Strategy (MDS) not supported
• 7.     Missing script editor and content editor web part.