Is PMTiles still a requirement at all?

[nlebovits]

Our current rule says vector datasets over 100 MB must ship a PMTiles copy for visualization. The June 26 meeting raised — without deciding — whether that should stay a hard requirement or be dropped to a recommendation.

Note that this thread is only about the requirement: we've separately settled how a PMTiles link should look when one exists (the web-map-links extension, ticket #569), and that shape stays valid either way.

---

Part of the July 2026 spec sprint. Hub: discussion #570 · work tracker: epic #564 · everything here carries the spec-sprint label.

[m-mohr]

It feels like the "overview in GeoParquet" is not mature enough and not widely adopted yet. Until then PMTiles seems to be good to have.

[cayetanobv]

I agree, geoparquet overviews is not mature enough. But I think this is the right path. Let's discuss the existing proposals and your thoughts regarding the portolan project.

[nlebovits]

Resolved as:

Visualization
Every geospatial collection MUST provide a way to render its data with zero infrastructure, either by rendering from source (the data asset is small and simple enough for clients to draw directly, e.g. a small GeoParquet, or a COG that is already display-ready, whether through an embedded color table or as a continuous raster colorized at draw time via the render extension and the required min/max statistics) or via a visualization derivative (an additional cloud-native product optimized for rendering, published as a collection-level asset with roles: [“visual”]; PMTiles is the recommended vector format today). A consumer decides by inspection: use a visual asset if present, otherwise render from source. Non-geospatial collections are exempt. Collections MUST include a thumbnail generated from default styling and MUST provide visualization styles as standalone STAC assets appropriate to the render path, except where the render path is self-rendering (a display-ready COG or a small GeoParquet drawn directly), which needs no separate style file.

Visualization Styles
When a collection provides a render path it MUST provide at least one style telling clients how to draw it, in a compatible format. For PMTiles that is a MapLibre GL style file (MapLibreGL style spec v8) in a styles/ subdirectory, with media type application/vnd.mapbox.style+json — a complete, self-contained JSON loadable directly by MapLibre GL JS. By convention such a file sets version 8, a human-readable name, sources.data.url as the relative path from styles/ to the PMTiles file (typically ../filename.pmtiles), and layers[].source to “data”.