How to check the SharePoint Online Version? While SharePoint does not have a version button or about box with version info, each version has a few distinctive features. Unfortunately, you won’t always see these features if an administrator and site designer has heavily customized the site.

If you see something that looks like your SharePoint environment, click the details below for more information about that version. There are a few ways to find out the version number.

Service CNF file

Service. cnf contains meta-information about the web. You can find more information about the List of Special Files and Directories.
To check the version with Service CNF and Browser Dev Tool that you have to log in to the SharePoint site and perform the following actions:

• Open your SharePoint site in a browser and add the next line to your URL: /_vti_pvt/service.cnf
  for example https://office365labs-admin.sharepoint.com/_vti_pvt/service.cnf
• Then you will see the value of vti_extenderversion: SR – this is the current version of SharePoint Online

Using Browser Developer Tools

The second option is to check the version using Browser Developer Tools; from your current browser, do the following actions:

• Open your browser and choose F12 to open Developer Tools
• Then go to your SharePoint Online page
• Next, go to headers
• Then look for init.js or core.js and check for Network SP Version

PowerShell

Another option is using with PowerShell command for that you have via the following actions:

• Open PowerShell with SharePoint Online Module
• Connect-PnPOnline https://domain.sharepoint.com //Connect to a SharePoint site
• Then it will return Client Side Object Model context details with SharePoint Version