Edit Mesh Modifier

Create or select an object > Modify panel > Modifier List > Object–Space Modifiers > Edit Mesh

Create or select an object > Modifiers menu > Mesh Editing > Edit Mesh

Tab panels > Modeling tab > Edit Mesh Modifier

The Edit Mesh modifier provides explicit editing tools for different sub-object levels of the selected object: vertex, edge, and face/polygon/element. The Edit Mesh modifier matches all the capabilities of the base Editable Mesh object, except that you cannot animate sub-objects in Edit Mesh. See Editable Mesh for a complete parameter reference.

When possible, it’s far more efficient and reliable to perform explicit modeling at the Editable Mesh level rather than store those edits within the Edit Mesh modifier. The Edit Mesh modifier must copy the geometry passed to it, and this storage can lead to large file sizes. The Edit Mesh modifier also establishes a topological dependency that can be adversely affected if earlier operations change the topology being sent to it.

There are, however, situations where using the Edit Mesh modifier is the preferred method.

You want to edit a parametric object as a mesh, but want to retain the ability to modify its creation parameters after the edit.
You want to store your edits temporarily within Edit Mesh until you are satisfied with the results, before committing them permanently to an editable mesh object.
You need to make edits across several objects at once, but do not want to convert them to a single editable mesh object.
You have a modifier in the stack that must remain parametric, and the mesh must be edited after the modifier is applied.