If you would like to use Netlify CMS to manage your site deployed to Vercel.

GitHub and Gitlab requires a server for authentication and Netlify provides this server only for sites deployed to it. Fortunately, such server is rather small and can work with Vercel's serverless functions.

In yours projects modify config.yml file:

backend:
  name: [github | gitlab]
  repo: adrian-ub/adrian-ub # Path to your Github/Gitlab repository
  branch: main # Branch to update
  base_url: https://netlify-cms.adrianub.vercel.app

• Create Github OAuth App:

  • Go to developer settings
  • Set Authorization callback URL to your deployed oauth website's callback URL: https://netlify-cms.adrianub.vercel.app/callback

• Create Gitlab OAuth app:

  • Go to User settings > Applications
  • Set Redirect URI to your deployed oauth website's callback URL: https://netlify-cms.adrianub.vercel.app/callback

• Set environment variables on Vercel

  OAUTH_GITHUB_CLIENT_ID=<you-client-id>
  OAUTH_GITHUB_CLIENT_SECRET=<you-client-secret>
  
  OAUTH_GITLAB_CLIENT_ID=<you-client-id>
  OAUTH_GITLAB_CLIENT_SECRET=<you-client-secret>

• Adrián UB (@AdrianUB)