When is it appropriate to use flexbox and grid for…

Flexbox and CSS Grid are designed for creating layouts.

Flexbox is better suited for:

One-dimensional layouts: Aligning and distributing elements in a single direction (row or column).
Inner alignment: Positioning elements inside a container horizontally and/or vertically.
Creating responsive components: Easily changing the direction and order of elements depending on the screen size.
Small groups of elements: Navigation menus, product cards, form elements.

.container-flex {
  display: flex; /* Defines the container as a flex container */
  justify-content: center; /* Aligns items horizontally to the center */
  align-items: center; /* Aligns items vertically to the center */
}

Grid is better suited for:

Two-dimensional layouts: Creating complex grids with simultaneous control over rows and columns.
Macro layout: Placing main page elements (header, sidebar, content, footer).
Creating complex responsive layouts: Easily defining areas and their placement for different screen sizes.
Full control over element placement: Precise positioning of each element within the grid.

.container-grid {
  display: grid; /* Defines the container as a grid container */
  grid-template-columns: 1fr 2fr 1fr; /* Defines 3 columns of different proportions */
  grid-template-rows: auto 1fr auto; /* Defines 3 rows */
  gap: 10px; /* Adds gaps between grid items */
}

.item {
  grid-column: 2; /* Places the element in the second column */
  grid-row: 1 / span 2; /* Places the element in the first row and spans 2 rows */
}

When to use together:

Grid for the main layout of the page (macro layout), and Flexbox for aligning elements inside grid cells (micro layout).
For example, grid to define the placement of the sidebar and content, and Flexbox to arrange elements inside the sidebar (navigation menu).

Summary table:

Capabilities	Flexbox	Grid
Measurement	One-dimensional	Two-dimensional
Main application	Inner alignment, components	Macro layout, complex grids
Control	Mainly along one axis	Along two axes simultaneously
Compatibility with other technologies	Good	Good

The choice depends on the task to be solved and the complexity of the required layout.

When is it appropriate to use flexbox and grid for layout?