Select an Image, Cover, Group, Table or Query Loop block and the toolbar offers Wide width and Full width beside the usual alignments.
What each one measures
| Alignment | Width |
|---|---|
| (none) | the content column — 640px by default |
| Wide | 900px |
| Full | the content width — 1170px by default |
Both come from theme.json, and Wide’s 900px is fixed there rather than following the Customizer. If you change the narrow width substantially, the gap between narrow and wide changes with it.
Full is not the window
This trips people up. In many themes Full width means edge-to-edge, no margins. In Stoat it means the container — the same width as the header bar and the footer — because a page whose images run past the masthead reads as two pages stacked.
Outside the container there is a 24px gutter (16px on a phone) that nothing crosses.
On a page already set to Full
If the page itself is set to Full, the content column is the container, so a Full block and an unaligned block are the same width. Wide then becomes narrower than the text around it, which is rarely what you want.
The pairing that works:
| Page width | Use |
|---|---|
| Narrow (the default) | unaligned for text, Wide for figures, Full for the occasional hero |
| Full | unaligned throughout; build structure with Columns and Groups instead |
Left and right alignment
Align left and align right float a block beside the text, with the text wrapping around it. They work, and they are worth using sparingly for a small portrait image beside a paragraph. Below the tablet width they drop to full width and stop floating, because a 200px float in a 340px column leaves nothing readable beside it.
In the editor
The canvas draws all three widths at the same proportions as the front end, so what you see while composing is what you get. On a post at the narrow width the canvas is the serif writing sheet; on anything at Full it is the full-width builder. See block editor support.