R44VC0RP/isocast

A free, open-source OBS alternative for Mac that records every source as its own file.

Isocast is a screen recorder and streaming app for macOS on Apple silicon. It works like OBS, with scenes, sources, transitions and an audio mixer, and it also saves each screen, window and camera as a separate full-quality file (ISO recording), all on one clock. It uses about half the CPU of OBS for the same recording, imports your OBS scene collections, and answers the obs-websocket tools you already use. Written in Rust, MIT or Apache 2.0. isocast.xyz

Download for Mac · Getting started · Isocast vs OBS · FAQ

• Every source in its own file. Fix a shot in your editor without re-recording: the program video plus one file per screen, window and camera, lined up by a session file. No plugin, no syncing by hand.
• Lighter on your Mac. In our benchmarks Isocast used 25–29% of a core where OBS used 58–71%, and 88–356 MiB of memory where OBS used 619–1344 MiB (how it was measured).
• Edit what you recorded. The editor window lays every ISO file out on one timeline: trim, split, switch angles and crop (9:16 too), then export frame-accurately without re-encoding what you didn't change, or hand the edit to Final Cut Pro, Premiere Pro or Resolve with every angle on its own track. Each project folder carries an .isoprj that reopens your edits anywhere.
• Bring your OBS setup. On first launch Isocast finds your OBS scene collections and profiles and imports them; anything that can't come over is listed with the reason. Tools that speak obs-websocket (Touch Portal, community Stream Deck plugins, obs-websocket scripts) work unchanged.
• Scriptable. The app, the isocast command and AI agents (over MCP) drive the same engine, so anything you can click you can automate.

OBS is the better choice today if you need Windows or Linux, a specific OBS plugin, Elgato's official Stream Deck actions, or years of proven polish. Isocast is for Mac users who want separate files per source, a lighter app, or a recorder they can script.

Isocast and OBS Studio 32.2.2 recording the same synthetic 1080p60 scene (left: MacBook Pro, M4 Max) and 4K60 scene (right: base M2 Mac mini) with hardware HEVC, median of 4 interleaved runs, October 2026. On the M2 4K run, OBS reported 3,904 frames skipped; only 1,645 of 6,292 were distinct. Synthetic sources, not real capture: see docs/benchmarks.md.

In Isocast 0.0.8 (the current download):

• Scenes and sources: screens, windows, cameras, microphones, desktop audio, one app's audio or everything but some apps (macOS 14.2+), pictures, videos (including WebM and MKV), text and web pages, with filters and an audio mixer.
• Transitions, including stingers with track mattes (WebM in VP8 or VP9, with transparency), and Studio Mode.
• ISO recording: any source as its own file, plus the program, with a .session.json that says where each file starts and where every scene switch and marker falls. Each ISO file can carry its own sound (the camera with the mic, the screen with desktop audio). Isocast warns before and during a take when this Mac can't keep up with every file, and suggests the closest setup that fits.
• Crash-safe takes: files are committed every half second, so a crash loses about 0.5 s, and they are repaired on the next launch. Pause and resume in the same file, and markers.
• The editor window (Window › Editor, ⌘E): every ISO track of your takes on one timeline, with trim, split, ripple delete, rolls, per-span angles, crops (free, 16:9, 9:16, 1:1, 4:5), waveforms, snapping, zoom, undo and frame-accurate export (a 9:16 file too). The takes are never changed. Playback has sound, in sync with the picture. Open Editor After Recording in Settings › Output opens it when you stop.
• Export for Final Cut Pro, Premiere Pro or DaVinci Resolve: File › Export writes a project that opens with every angle on its own track, cut like your Isocast edit and pointing at your original files (no re-encoding), with crops, markers and each source's audio.
• Project files: every project folder has a <name>.isoprj with its takes and edits. Copy the folder anywhere and double-click the file to reopen it in the editor; File › Open and Open Recent.
• Projectors and multiview: the program, preview, any scene or any source full screen on another display or in a window, and an OBS-style multiview with tally (red program, green preview).
• A canvas for every destination: up to eight canvases besides the main one (a 9:16 vertical, a square, a story), each with its own size, frame rate, scene layouts, recording and stream destinations, so 16:9 goes to Twitch while 9:16 goes to Shorts. Each has its own replay buffer, virtual camera, projectors and multiview tiles.
• Advanced masks: shape masks (rounded rectangle, circle, polygon, star, heart) with soft edges and handles on the picture, gradient masks, and source masks that use any source or scene, a video included, as a live mask. They stack and animate.
• Audio interfaces: pick a microphone source's inputs (one input records as centred mono at full level) and a Mono switch per source. Interfaces with more than two inputs record inputs 1 + 2 by default.
• Replay buffer: keep the last 5–300 seconds of the program in memory and save them with a click or a hotkey.
• Virtual camera: the program as a camera for Zoom, Meet, FaceTime and other apps, updated with the app, and Remove Virtual Camera when you're done with it.
• Streaming to Twitch, YouTube, Kick, Facebook or any RTMP/RTMPS server, or to several at once, each with its own key kept in your Keychain. Starting a stream during a recording no longer drops ISO frames.
• First launch finds your OBS scene collections and offers to import them, then Optimize picks settings this Mac can keep up with, for recording, streaming or both, from a measured profile of this Mac.
• Automatic quality: while you record or stream, a governor steps down streams, previews and extra canvases when the Mac falls behind and back up when it recovers, never your program or ISO files. Settings you pin stay put.
• Recording targets: next to Record, choose whether a recording starts a new project or adds a take to the current timeline.
• obs-websocket v5 compatibility (isocast websocket enable), so OBS remotes, Touch Portal, community Stream Deck plugins and obs-websocket scripts (obs-cmd, obsws-python) can drive Isocast.
• Profiles and scene collections, as in OBS, global hotkeys, timelines (record takes in order, export one video), the isocast CLI and MCP tools for agents.
• A warning when another app or a busy or hot Mac threatens the recording, before frames drop.
• Automatic updates. macOS prompts name the engine "Isocast Engine".

Coming next (not in a release yet; see coming soon):

• Windows: recording works end to end in testing (screen, camera and microphone to the program and ISO files, with previews); streaming, media playback and an installer release come next.
• Later ideas: running real OBS plugins in a helper process, Elgato Stream Deck's own protocol, shader filters and WebAssembly sources.

Every source in its own file. One take: the program video, an ISO file per source and the session file that lines them up.

Studio Mode. Line up the next scene in the preview while the program stays on air, then take it live with a cut, a fade or a stinger.

Multiview. The preview, the program and every scene in one window, with a red tally on what's on air and green on what's next.

A vertical canvas beside the main one. The same sources laid out for 9:16, recorded and streamed alongside the main canvas.

More canvases, one per platform. Beyond the vertical one, add canvases for Shorts, a square feed or anything else, each with its own size, frame rate, scenes and stream destinations. The canvas monitor's menu switches between them, and Settings › Video › Canvases sets them up.

Masks. Show a source inside a shape (a circle, star, heart, polygon or rounded rectangle) with handles on the picture to move, size and turn it, or let another source's live picture, such as a video, decide what shows.

Edit every angle. The editor window shows a track per ISO source under the program; trim, split, pick the angle for each stretch, crop it (9:16 too) and export.

Choose what gets its own file in Settings › Output.

Stream to several places at once. Settings › Stream lists each destination with its own key, on or off.

Bring your OBS scenes: on first launch Isocast offers the scene collections it finds, then Optimize picks settings this Mac can keep up with.

Tuned to your Mac. Isocast measures this Mac once, quietly, and Optimize uses that machine profile to choose settings it can keep up with. While you record or stream, Automatic Quality lowers only what you allow (the preview's refresh, the vertical canvas's frame rate, a stream's bitrate) when this Mac falls behind, says why in Settings, and puts it all back once the load passes.

Script it. The isocast command drives the same engine as the app.

1. Get the latest Isocast.dmg from Releases.
2. Open it and drag Isocast to Applications.
3. Isocast updates itself: it checks daily and asks before installing, or use Isocast › Check for Updates….

You need a Mac with Apple silicon (M1 or later) and macOS 14 Sonoma or later. Intel Macs aren't supported.

Isocast is in alpha: expect rough edges, and keep a backup recorder for anything you can't redo.

1. Open Isocast and allow access. The permissions step asks for screen recording, camera and microphone access; macOS may ask you to reopen Isocast after granting screen recording.
2. Pick a start. Start with this Mac builds ready-made scenes from your screen, camera and microphone. Import from OBS brings an OBS scene collection over.
3. Record. Press Start Recording, then Stop. File › Show Recordings opens the folder.

More in Getting started.

Can I import my OBS scenes? Yes. Import from OBS (or isocast setup import-obs) reads OBS scene collections and profiles from ~/Library/Application Support/obs-studio or an exported .json, and lists anything without an Isocast equivalent. The OBS parity table shows how each OBS source, filter and transition maps.

Does it work with my Stream Deck? Through obs-websocket. Run isocast websocket enable; it prints the address (ws://127.0.0.1:4455) and a password once. Enter both in the tool's OBS WebSocket settings: Touch Portal, Streamer.bot, Bitfocus Companion, community Stream Deck plugins that use obs-websocket, or scripts like obs-cmd. Elgato's official Stream Deck OBS actions use their own OBS plugin rather than obs-websocket, so they don't connect.

Does it support stingers and WebM? Yes: stinger transitions with track mattes, and WebM (VP8 or VP9, with transparency) and MKV files in media sources and stingers, so older OBS stingers in VP8 work too. Stinger audio isn't played yet.

Can I edit in Isocast? Yes, the basics. Record takes into a timeline, then open the editor (Window › Editor, ⌘E) to trim, split, delete spans and choose which ISO angle shows when. Export is frame-accurate and copies the video as recorded except near a cut; the original files are never changed. For effects, colour and titles, open the ISO files in your usual editor.

Can it stream to Twitch or YouTube? Yes: Twitch, YouTube, Kick, Facebook or any RTMP/RTMPS server, or several at once, while recording if you like. See Streaming.

Where do my recordings go? To ~/Movies/Isocast unless you choose another folder in Settings › Output, one folder per recording. Each take holds the program video, one file per ISO source (SCREEN-…, CAMERA-…) and a .session.json. Files are committed every half second, so a crash loses about the last 0.5 s, and Isocast repairs the files on its next launch (a power cut can lose more; nothing is guaranteed then). More on crash-safe takes.

Is it free? Is it open source? Yes and yes: free, MIT or Apache 2.0. It's a new app written in Rust, not a fork of OBS, and no OBS code was read or copied.

Does it work on Windows or Linux? Not yet. Mac first; the engine is built so other platforms can follow.

• Getting started, recording, streaming
• Timelines: record takes in order and export one video
• Hotkeys, scenes as code, plugins
• References: CLI, setup files, MCP tools for agents
• Benchmarks against OBS, OBS parity, coming soon

Building from source, how it works inside, and how to contribute: CONTRIBUTING.md. Licensed under MIT or Apache 2.0; third-party licences are in THIRD_PARTY_NOTICES.