deltamap/default_tile_sources.toml

[[tile_sources]]
name = "OSM"
max_zoom = 19
url_template = "http://a.tile.openstreetmap.org/{z}/{x}/{y}.png"
extension = "png"

[[tile_sources]]
name = "esri"
max_zoom = 19
url_template = "https://server.arcgisonline.com/arcgis/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}"
extension = "jpg"