Trailish

Trailish is a software framework and data standard for representing and working with trail networks used in outdoor recreation. It provides a compact, interoperable model for describing routes, waypoints, elevation data, and associated metadata such as surface type, difficulty, accessibility, and seasonal restrictions. Trailish emphasizes offline functionality, modular design, and compatibility with common geospatial formats, enabling developers to build planning, navigation, and maintenance tools for hikers, cyclists, and mountaineers.

Trailish originated as an open-source project in the late 2010s, driven by contributors from the geospatial and outdoor communities. It has matured through community-driven releases and interoperability efforts with GPX, GeoJSON, and existing map tile ecosystems. Implementations exist in multiple languages, with a reference specification and a lightweight runtime for browser and server environments.

The data model centers on a trail network graph. Nodes represent junctions or points of interest, while edges represent trail segments with attributes such as length, elevation gain, slope, surface, and difficulty. Elevation profiles can be embedded or generated from digital elevation models. The rendering component supports vector overlays, offline tile caches, and simple route planning that accounts for elevation and constraints. APIs typically allow importing common formats, exporting to Trailish-compatible formats, and extending the model with domain-specific metadata.

Trailish is used by mapping apps, park and land-management agencies, conservation groups, and NGOs for planning routes, recording maintenance, and sharing trail data. The project is released under the MIT License and is maintained by a community of contributors with governance through public discussions and repository contributions.