JustGetIt

A modern multi-connection download manager for macOS 26 on Apple Silicon. Built with SwiftUI and Liquid Glass, Swift 6 strict concurrency, and SwiftData.

Design

JustGetIt is written in pure Swift with no external dependencies. It is built around three goals: performance, reliability, and long-term maintainability. To serve those goals the scope is deliberately narrow, which keeps the codebase small and easy to reason about, and keeps the maintenance burden low. Today it does one thing well, downloading files from URLs that do not require authentication. More capabilities may follow, but the guiding idea stays the same: just get it.

Features

• Multi-connection downloads. Files are split into byte-range chunks fetched over many parallel connections (HTTP Range requests) and written to per-offset file handles in a single pre-allocated file.
• Work-stealing. The file is divided into more chunks than connections, so when a fast connection finishes it pulls the next pending chunk and no connection sits idle.
• Resume. Per-chunk offsets are checkpointed to SwiftData, and paused or interrupted downloads continue with a Range request plus If-Range validation, so a changed file restarts cleanly.
• Concurrent queue. A configurable limit controls how many downloads run at once, and the rest wait their turn.
• Transient error handling. Server responses such as 429 and 503 are retried with jittered exponential backoff, honoring Retry-After.
• Global hotkey. A configurable, system-wide shortcut (default Cmd+Opt+Shift+D) starts downloading every URL on the clipboard.
• Disk safety. A missing folder is created, a full disk is caught up front when the size is known, and out-of-space writes fail cleanly.
• Liquid Glass UI. A sortable table, color-coded status, file-type icons, a floating glass stats bar, and a menu-bar popover with live progress.
• Notifications on completion and failure.

Installation

1. Download the latest release: JustGetIt.dmg.

2. Open the DMG and drag JustGetIt into your Applications folder.

3. JustGetIt is ad-hoc signed rather than notarized, so macOS quarantines it after download. Clear the quarantine flag once, then open the app normally:

   xattr -cr /Applications/JustGetIt.app

Requirements

• macOS 26 or later on Apple Silicon
• Xcode 26 or later
• xcodegen (brew install xcodegen)
• create-dmg for packaging (brew install create-dmg)

Build and run

xcodegen generate      # regenerate JustGetIt.xcodeproj from project.yml
open JustGetIt.xcodeproj
# press Cmd+R in Xcode, then Cmd+N to add a download URL

Package a DMG

./make-dmg.sh

This builds a Release, ad-hoc signed app and packages it as JustGetIt.dmg. Ad-hoc signing runs locally without a Developer ID or notarization, so on first launch you right-click the app and choose Open once to clear Gatekeeper.

Every push to main and every published release also builds the DMG in CI (see .github/workflows/build.yml). Release builds attach the DMG to the release.

Architecture

DownloadEngine (actor)          owns the URLSession, the connection budget, and every
  ConnectionGate (actor)        active coordinator. Publishes an AsyncStream of events
  RemoteProbe                   the UI consumes.
  SegmentDataDelegate           URLSession delegate feeding per-task AsyncThrowingStreams.
  DownloadCoordinator (actor)   a worker pool pulls chunks from a pending queue
                                (work-stealing), retries stalls, and writes each chunk
                                to its offset in the .download file.

AppModel (MainActor, Observable)  bridges engine events to rows, persists records
                                  (SwiftData), runs the concurrency queue, and notifies.

Engine smoke tests

.smoketest/SmokeTest.swift exercises the engine headlessly and verifies the reassembled file against a known SHA-256. .smoketest/FlakyServer.swift is a small localhost server used by the retry test, which confirms the engine retries transient 503 responses (honoring Retry-After) and still reassembles the file byte for byte.

SDK=$(xcrun --sdk macosx --show-sdk-path)
swiftc -sdk "$SDK" -target arm64-apple-macos26.0 \
  Sources/Models/Models.swift Sources/Engine/*.swift \
  .smoketest/SmokeTest.swift .smoketest/FlakyServer.swift \
  -o .smoketest/enginetest
./.smoketest/enginetest [connections] [url] [expectedSHA256]
./.smoketest/enginetest retry

License

MIT. See LICENSE.