Bootstrap Grid, do I need a container?

Update Bootstrap 4

Outermost rows should also be wrapping in container or container-fluid in Bootstrap 4 to prevent horizontal scolling caused by negative margins on the .row.

Bootstrap 3

You should wrap row in container or you'll have a problem with the negative margins that BS 3 uses for the row element. Basically the row is designed to be within a container. Read more on the Bootstrap grid

Play with this example on Bootply: http://bootply.com/83751

According to the latest documentation:

https://getbootstrap.com/docs/5.1/layout/gutters/#no-gutters

it is reasonable to drop the outer container (or at least its css class assignment):

Need an edge-to-edge design? Drop the parent .container or .container-fluid.

This appears to have been in the documentation since the 4.0 release: https://getbootstrap.com/docs/4.0/layout/grid/