The browser tab icon is a site.keys.favicon value in antora-playbook.yml, served
from a file under ui.supplemental_files:
site:
keys:
favicon: /_/favicon.ico
ui:
supplemental_files: ./supplemental-uidocouture new already wires this up with a placeholder — replace
docs/supplemental-ui/favicon.ico with a real one, same filename, and rebuild. The
// prefix is the UI bundle’s own output directory (ui.output_dir, default ),
not the site root — supplemental files land there, which is why the key isn’t just
/favicon.ico.
What actually reads at that size
A favicon renders at 16–32px in a browser tab — full logo artwork (fine detail,
gradients, a wordmark) turns to mush at that size. Use a flat, single-colour
simplified mark instead: the product symbol alone (drop any text), filled solid in
black, white, or the brand’s own solid accent — no gradients, no thin strokes. The
seeded placeholder is a multi-res .ico (16×16 + 32×32 embedded); that’s still the
safest container since browsers pick whichever embedded size fits, though a plain PNG
works too — head-icons.hbs only ever emits a single <link rel="icon">, regardless
of format.
Using a different filename
Rename the file under supplemental-ui/ and update site.keys.favicon to match — the
path is a literal, not a convention Antora infers.