Hydra

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Multithreaded download manager for macOS with browser-session passthrough.

Downloads files in several parallel streams (HTTP Range) and replays your authenticated browser session across every stream — so it downloads faster, and downloads what only you can access. Lives in the menu bar, pairs with the browser on its own, no copying ids or editing configs.

macOS 13+ · Swift · native SwiftUI/AppKit

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Features

• Multithreaded downloads — the file is split into blocks, a connection pool pulls them in parallel (HTTP Range). Speed, ETA and thread count in real time.
• Session passthrough — the extension captures Cookie, User-Agent, Referer for the link and replays them in every stream. Grabs what sits behind a login.
• Pause / resume that survives a restart — the done-blocks bitmap is written to disk; quit with an unfinished download → reopen → it continues from the same spot.
• Defrag block grid — the whole file at a glance: done, downloading now, ahead, and "X / Y blocks".
• Queue — concurrent-download limit, the rest wait; priority, pause-all.
• History — completed downloads persist across launches, with search and "Show in Finder".
• Browser capture — auto-capture by rules (size, file types) or "Download with Hydra" in the context menu.
• Floating drop window — always on top; drag a link from anywhere onto it.
• Native notifications — completion, error (with "Retry"), sign-in required.
• Update check — notifies on launch when a newer release is on GitHub; manual check in Settings/menu.
• Native macOS look — system accent, materials/vibrancy, SF, dark/light theme.
• Localized — English, Russian, Chinese; switch in Settings → System → Language.

Why Hydra?

A free, open-source download accelerator for macOS — a native alternative to IDM, Folx and JDownloader, without the price tag or the Java runtime.

	Browser built-in	Typical download managers	Hydra
Multithreaded (HTTP Range)	❌	✅	✅
Replays your logged-in session	❌	⚠️ partial	✅ cookies + UA + referer
Downloads files behind a login	❌	⚠️	✅
Pause / resume across restart	⚠️	✅	✅ block-level
Native menu-bar app	—	varies	✅ SwiftUI / AppKit
Open source, free	—	usually paid	✅ MIT

Screenshots

Menu-bar popover	Download details (multithreaded)

Downloads window	Per-download actions

Settings	Floating drop circle

How it works

Browser ──(link capture + session)──▶ Extension
                                          │ native messaging
                                          ▼
                                    hydra-host  ──(Unix socket /tmp/hydra.sock)──▶ Hydra.app
                                     (fallback: downloads itself if app isn't running)   │
                                                                                          ▼
                                                                                   DownloadCore
                                                                          probe → blocks → N streams → assemble

• Automatic pairing, no user steps. The Chrome id is pinned by a key in the manifest (deterministic hfdmeoleepighofjiookfjcjekoopaim), and Hydra.app registers the native-messaging host into every browser on launch. No copying ids, no install.sh.
• Two engine cores: ResumableDownload (block-based, pause/resume — for the app) and Downloader (contiguous chunks, fire-and-forget — for the CLI and the host fallback). Both covered by byte-exact tests.

Install

Homebrew (easiest)

brew install --cask --no-quarantine pushipu/tap/hydra

--no-quarantine is needed while the app is ad-hoc signed (not notarized yet); it lets the app open without Gatekeeper warnings. Then continue from step 2 below.

Manual

1. Download the latest Hydra-*-macos.zip from Releases, unzip, move Hydra.app to /Applications, launch once — it registers the host into every installed browser.
2. Install the extension for your browser — the app bundles both. Open Settings → Capture → Install extension (or the menu-bar menu → "Install extension…"); Finder opens the bundled chrome/ folder and hydra-firefox.xpi:
   • Chrome / Brave / Edge: chrome://extensions → Developer mode → "Load unpacked" → the chrome/ folder.
   • Firefox: about:debugging → "Load Temporary Add-on" → hydra-firefox.xpi.
   • Safari: manual via Xcode for now (docs/SAFARI_SETUP.md).
3. Done — cookies/session and multithreading work right away.

Distributing to other machines requires notarization (Developer ID). Locally an ad-hoc signature is enough — Hydra.app launches on your own machine without warnings.

Build from source

Requires the Xcode/Swift toolchain and rsvg (for icons: brew install librsvg).

./build-all.sh

Drops into dist/: Hydra.app (host embedded, self-registering), chrome/ (unpacked extension), hydra-chrome.zip, hydra-firefox.xpi.

Version is single-sourced from the VERSION file: the build stamps it into the app's Info.plist and every extension manifest (CFBundleVersion = git commit count). Bump VERSION, rebuild — app and extensions stay in lockstep.

cd core && swift test          # engine tests (byte-exact, resume, filename sanitizing)
.build/release/hydractl URL --out ~/Downloads --connections 8   # CLI

Layout

core/Sources/
  DownloadCore/   engine: probe, blocks, resume, session, rate limit, history
  HydraApp/       SwiftUI/AppKit: popover, window, settings, drop zone, notifications
  hydractl/       CLI
  hydra-host/     native messaging host (delegates to app, fallback — downloads itself)
extension/        WebExtension (Chrome/Firefox), pinned key, pairing-status popup
app/build.sh      builds Hydra.app (signing, host embedding, icon)
build-all.sh      ⭐ everything at once → dist/
docs/             ARCHITECTURE.md, SAFARI_SETUP.md, USAGE.md, screenshots/

Browser extension

A thin layer: captures the session, intercepts links, shows the pairing status with the app and the list of current downloads. The logic and UI live in the app. Capture settings (auto-capture, min size, file types, threads) have a single source of truth in the app; the extension reads them through the host.

FAQ

Is Hydra a free IDM / Folx alternative for macOS? Yes — open-source (MIT), multithreaded, with browser-session passthrough, native to macOS.

How does it download files that are behind a login? The browser extension captures your Cookie, User-Agent and Referer for the link and replays them on every parallel connection, so the server sees your authenticated session.

Which browsers are supported? Chrome, Brave, Edge and Firefox via extensions. Safari needs a manual setup for now.

Is it safe? What does the extension read? It reads cookies only to pass your existing session to the downloader. Nothing is sent anywhere except to the file's own server — there is no telemetry.

Does pause/resume survive a restart? Yes. The done-blocks bitmap is persisted to disk, so you can quit mid-download and continue later.

macOS says the app "cannot be opened" — why? It's ad-hoc signed and not notarized yet. Right-click the app → Open, or install via Homebrew with --no-quarantine.

License

MIT © pushipu