The same viewport in MapLibre will render one zoom level lower in Leaflet maps.
For example 4/40/-100 on osm.org(leaflet) vs americanamap.org(maplibre)
https://www.openstreetmap.org/#map=4/40.00/-100.00
vs
https://americanamap.org/#map=4/40/-100
In MapSwap I deal with this by templating the URLs for MapLibre-style zoom with {z} and those for Leaflet-style zoom with {Z} and replacing {Z} with zoom+1 rather than zoom (this means MapSwap operates on a MapLibre-style zoom level. You may want to go the other way and interpret the zoom as Leaflet-style)
The same viewport in MapLibre will render one zoom level lower in Leaflet maps.
For example 4/40/-100 on osm.org(leaflet) vs americanamap.org(maplibre)
https://www.openstreetmap.org/#map=4/40.00/-100.00
vs
https://americanamap.org/#map=4/40/-100
In MapSwap I deal with this by templating the URLs for MapLibre-style zoom with
{z}and those for Leaflet-style zoom with{Z}and replacing{Z}withzoom+1rather thanzoom(this means MapSwap operates on a MapLibre-style zoom level. You may want to go the other way and interpret the zoom as Leaflet-style)