A complete style URL, like
mapbox://styles/mapbox/streets-v12, is comprised of three components:
mapbox://styles: points to the Mapbox Styles API
/mapbox: your Mapbox username
/streets-v12: your style's unique ID
You can find the style URL on your Styles page in Mapbox Studio. Click on the menu next to a style to reveal its style URL. Click the icon to copy the style URL.
For each custom style you create in Mapbox Studio, there is a draft and a production style URL available. If you are using the draft version of your style,
/draft will also be appended to the end of the style URL.