New Block Kit layout block
By Steven Van ·
Developers can place section, image, actions and table blocks side by side in one grid, and older Slack clients show fallback blocks.
Slack has added a layout block to Block Kit. It arranges other blocks into a grid of rows and side-by-side items, so a single message or view can show multi-column content instead of one vertical stack.
What it is for
Slack points to summaries, detail panes and metric strips, anywhere a column of stacked blocks would waste horizontal space. Related fields can sit next to each other instead of being stacked, which Slack says makes output denser and easier to scan.
How it works
- Existing blocks drop in. Section, image, actions, table and other blocks can go inside a layout item with no changes.
- Layout hints. Items are declared as narrow, standard or wide, and Slack handles the rest rather than requiring pixel measurements.
- Self-contained. The grid lives entirely inside one block, so reordering the parent blocks array won't break it.
- Fallback. Older clients render the fallback blocks you supply.
The linked Block Kit overview does not cover the layout block's JSON fields. It describes blocks as the components stacked in a blocks array, with up to 50 blocks per message and 100 in modals or Home tabs.