PMTiles

PMTiles is a single-file archive format for tiled data. A PMTiles archive can be hosted on a commodity storage platform such as S3, and enables low-cost, zero-maintenance map applications that are "serverless" - free of a custom tile backend or third party provider.

• Protomaps Blog: Dynamic Maps, Static Storage

• PMTiles Inspector - inspect and preview PMTiles local or remote PMTiles archives. Archives on cloud storage may require CORS for the origin https://protomaps.github.io.

• Raster Tiles Demo (OSM Carto)

• Vector Tiles Example (US Zip Codes)

Demos require MapLibre GL JS v1.14.1-rc.2 or later

See also:

• Cloud Optimized GeoTIFFs

How To Use

JavaScript

See js/README.md for usage in Leaflet or MapLibre GL JS.

Go

See https://github.com/protomaps/go-pmtiles

Python

pip install pmtiles
pmtiles-convert TILES.mbtiles TILES.pmtiles
pmtiles-convert TILES.pmtiles DIRECTORY
pmtiles-show TILES.pmtiles // see info about a PMTiles directory
pmtiles-serve TILES.pmtiles // start an HTTP server that decodes PMTiles into traditional Z/X/Y paths

See https://github.com/protomaps/PMTiles/tree/master/python/bin for library usage

Serverless

PMTiles on AWS Lambda

PMTiles on Cloudflare Workers

Specification

PMTiles is a binary serialization format designed for two main access patterns: over the network, via HTTP 1.1 Byte Serving (Range: requests), or via memory-mapped files on disk. All integer values are little-endian.

A PMTiles archive is composed of:

• a fixed-size 512,000 byte header section
• Followed by any number of tiles in arbitrary format
• Optionally followed by any number of leaf directories

Header

• The header begins with a 2-byte magic number, "PM"
• Followed by 2 bytes, the PMTiles specification version (currently 2).
• Followed by 4 bytes, the length of metadata (M bytes)
• Followed by 2 bytes, the number of entries in the root directory (N entries)
• Followed by M bytes of metadata, which must be a JSON string with bounds, minzoom and maxzoom properties (new in v2)
• Followed by N * 17 bytes, the root directory.

Directory structure

A directory is a contiguous sequence of 17 byte entries. A directory can have at most 21,845 entries. A directory must be sorted by Z, X and then Y order (new in v2).

An entry consists of:

• 1 byte: the zoom level (Z) of the entry, with the top bit set to 1 instead of 0 to indicate the offset/length points to a leaf directory and not a tile.
• 3 bytes: the X (column) of the entry.
• 3 bytes: the Y (row) of the entry.
• 6 bytes: the offset of where the tile begins in the archive.
• 4 bytes: the length of the tile, in bytes.

All leaf directory entries follow non-leaf entries. All leaf directories in a single directory must have the same Z value. (new in v2).

Notes

• A full directory of 21,845 entries holds exactly a complete pyramid with 8 levels, or 1+4+16+64+256+1024+4096+16384.
• A PMTiles archive with less than 21,845 tiles should have a root directory and no leaf directories.
• Multiple tile entries can point to the same offset; this is useful for de-duplicating certain tiles, such as an empty "ocean" tile.
• Analogously, multiple leaf directory entries can point to the same offset; this can avoid inefficiently-packed small leaf directories.
• The tentative media type for PMTiles archives is application/vnd.pmtiles.

Implementation suggestions

• PMTiles is designed to make implementing a writer simple. Reserve 512KB, then write all tiles, recording their entry information; then write all leaf directories; finally, rewind to 0 and write the header.
• The order of tile data in the archive is unspecified; an optimized implementation should arrange tiles on a 2D space-filling curve.
• PMTiles readers should cache directory entries by byte offset, not by Z/X/Y. This means that deduplicated leaf directories result in cache hits.

Recipes

Example of how to create a PMTiles archive from the Census Bureau Zip Code Tabulation Areas Shapefile using tippecanoe and the pmtiles-convert python program:

    # use GDAL/OGR to convert SHP to GeoJSON
    ogr2ogr -t_srs EPSG:4326 cb_2018_us_zcta510_500k.json cb_2018_us_zcta510_500k.shp
    # Creates a layer in the vector tiles named "zcta"
    tippecanoe -zg --projection=EPSG:4326 --no-tile-compression --no-feature-limit --no-tile-size-limit -o cb_2018_us_zcta510_500k_nolimit.mbtiles -l zcta cb_2018_us_zcta510_500k.json
    pmtiles-convert cb_2018_us_zcta510_500k_nolimit.mbtiles cb_2018_us_zcta510_500k_nolimit.pmtiles

For uploading your PMTiles to cloud storage, rclone is recommended:

rclone config
rclone copy my_archive.pmtiles my_destination:my_folder --progress --s3-chunk-size=256M

License

The reference implementations of PMTiles are published under the BSD 3-Clause License. The PMTiles specification itself is public domain, or under a CC0 license where applicable.