---
title: "DropletEnvironmentService, DroppyKit"
description: "Read-only facts about the host and the machine it is running on."
canonical: "https://getdroppy.app/docs/droppykit/api/droplet-environment-service"
last-updated: "2026-09-09"
---

# DropletEnvironmentService

Read-only facts about the host and the machine it is running on.

`@MainActor protocol DropletEnvironmentService : AnyObject`

## Properties

### appVersion

`@MainActor var appVersion: String { get }`

Marketing version of the running Droppy, for example `"15.2.2"`.

### containerDirectory

`@MainActor var containerDirectory: URL { get }`

A private, per-droplet directory that persists across updates. Create it lazily; the host guarantees the parent exists.

### didChange

`@MainActor var didChange: AnyPublisher<Void, Never> { get }`

Fires whenever `notchGeometry` or `surfaceAppearance` changes.

### dropletCallbackURL

`@MainActor var dropletCallbackURL: URL? { get }`

Base URL for callbacks to this droplet in this host, or `nil` when external URL delivery is unavailable. Append your route, for example `dropletCallbackURL?.appendingPathComponent("settings")`, instead of hardcoding Droppy's scheme. Playground uses its own scheme so replies reach the development app. Requires API 1.20.0.

### isHarness

`@MainActor var isHarness: Bool { get }`

Whether this process is the local development harness rather than Droppy itself. Prefer feature detection over branching on this; it exists for diagnostics and for demo data in previews.

### notchGeometry

`@MainActor var notchGeometry: DropletNotchGeometry { get }`

Geometry of the notch surface the droplet is currently rendered on.

### surfaceAppearance

`@MainActor var surfaceAppearance: DropletSurfaceAppearance { get }`

The appearance on the target display described by `notchGeometry`. Every shell is Dark: a physical-notch shell, an island and the notch shape on a display without a camera, in either system appearance. This service is shared by all of a droplet's views. A view mounted on several displays uses its inherited `colorScheme` or adaptive colour tokens for drawing, so each mount resolves its own appearance.