Difference between @material-ui vs material-ui (without at-sign)

The @ scope indicates package ownership

The main advantage of scopes I've seen so far is that each scope is controlled by npm account of an organization / user, much like GitHub usernames / organization names.

This way, it makes it easy to determine if the package you are looking at belongs to an organization you trust, or if it is a third party tool.

For example, if you see:

@material-ui

then you know that it comes from the material-ui team and can be trusted.

On the other hand, the same could not be said about:

material-ui

For more https://docs.npmjs.com/about-scopes

@material-ui/core is the correct one to use for v4. For v5, the equivalent package is @mui/material.

If you go to https://www.npmjs.com/package/material-ui, you'll see that material-ui is deprecated. The last stable version in the material-ui package was 0.20.2. For the 1.0 release it moved to @material-ui/core and for the stable release of v5 it moved to @mui/material.

The @material-ui scope (for v4) is used for the following packages that are all managed within the monorepo you referenced (https://github.com/mui-org/material-ui/tree/v4.12.3/packages):

• @material-ui/core
• @material-ui/icons
• @material-ui/styles
• @material-ui/system
• @material-ui/lab
• @material-ui/utils
• @material-ui/types
• @material-ui/docs
• @material-ui/codemod

Similarly, the @mui scope (for v5) is used for the similar set of packages supported for v5 (https://github.com/mui-org/material-ui/tree/master/packages):

• @mui/material
  • This is the equivalent of @material-ui/core
• @mui/core
  • This is the NOT the equivalent of @material-ui/core. @mui/core is a new package for unstyled (no Material-Design CSS applied) versions of the components.
• @mui/icons-material
• @mui/styles
  • This is for supporting the withStyles and makeStyles JSS-backed styling APIs and is not recommended for use in new projects.
• @mui/system
• @mui/lab
• @mui/utils
• @mui/types
• @mui/docs
• @mui/codemod