Who Compositor is for#
Designers compositing photos on Apple silicon Macs
Compositor's layer system, blend modes, adjustment layers, and layer effects cover the full standard compositing workflow. Photoshop keyboard shortcuts carry over directly, so a designer can move their existing muscle memory to a free, MIT-licensed tool without relearning the interface.
Skip if:
If your team works across macOS and Windows, Compositor does not run on Windows. If you need CMYK output or rely on Photoshop features beyond compositing and post-processing, gaps may require keeping Photoshop available.
Photographers doing post-processing and retouching
The Camera Raw filter covers light, color, curves, and geometry in a panel beside the canvas. Spot Healing Brush, Clone Stamp, and Content-Aware Fill handle retouching. Levels, Curves, Hue/Saturation, Exposure, and Gradient Map are available both as adjustment layers and as direct adjustments.
Skip if:
If your workflow centers on catalog management or batch processing a large library, Compositor is a per-image editor with no built-in catalog or batch-export feature.
Developers building AI image pipelines on macOS
The .comp project format is a folder of PNG layers and a manifest that AI agents and scripts can read and write directly. An open project updates live as the folder is modified, making Compositor scriptable in ways no commercial image editor supports natively.
Skip if:
If your AI pipeline targets Linux or needs to run on a server without a display, the .comp format can be assembled without Compositor's UI, but the app itself requires macOS 26 on Apple silicon.
Swift developers and open source contributors
The full Xcode project is available under MIT. Swift developers can add features, fix bugs, or port workflows directly in the codebase. The release script handles signing, notarization, and DMG packaging, lowering the barrier to shipping a modified build.
Skip if:
If you need a shipping image editor today and do not intend to build from source, downloading the pre-built release from GitHub Releases is the right path.
The problem it solves#
Adobe Photoshop requires an ongoing subscription to use. For Mac users who need professional image editing for compositing and post-processing, the cost is the primary friction.
Mac users doing this kind of work are left choosing between an ongoing subscription, a paid proprietary product like Affinity Photo 2, or learning a different editing paradigm. GIMP is free but its interface conventions differ enough from Photoshop's that switching means relearning keyboard shortcuts, the layer panel, and the muscle memory that Photoshop users have built over years.
How it solves it#
Photoshop-compatible layer system
Layers and folders with Photoshop's full set of blend modes in Photoshop's order. Folder opacity dims everything inside it. Layer masks are paintable, fillable, invertable, blurrable, and featherable anywhere on the canvas, past the layer's own pixels. Adjustment layers include Hue/Saturation, Levels, Curves, Exposure, Gradient Map, Grain, Black and White, Color Balance, Invert, Gaussian Blur, Motion Blur, and Noise.
Camera Raw filter with full control panel
Applies a Camera Raw filter with controls for light, color, curves, color mixer, color grading, detail, optics, and geometry, displayed in a panel beside the canvas. Live previews apply within any active selection, so you can adjust a masked region without affecting the whole image.
PSD and PSB import with editable layers
Opens 8-bit RGB Photoshop files and keeps folders, masks, blend modes, fill shapes, and simple horizontal text editable rather than flattening them. A conversion report appears before anything is applied. Large PSD files too big to open have their layers cropped to the canvas instead of refusing to open.
Content-Aware Fill and Object selection
Content-Aware Fill removes objects from a photo and fills the gap by synthesizing surrounding pixels. It can also extend a canvas beyond its current edges. Object selection (part of the Magic tool, toggled with Tab) traces whatever you click, so isolating a subject does not require a freehand selection.
Non-destructive transform and GPU layer effects
Move, scale, rotate, and flip operations preserve the layer's full original resolution however small you make it. Layer effects (Stroke, Drop Shadow, Color Overlay, Inner Shadow, Outer Glow, Inner Glow) are rendered on the GPU and remain editable at any time without re-flattening the layer.
AI-agent-editable .comp project format
A .comp project is a folder of PNG layers and a manifest file. AI agents and scripts can build or modify projects by writing to that folder structure, and an open project in Compositor updates live as files change. The format specification is documented in the repository at docs/writing-comp-files.md.
Strengths and trade-offs#
Strengths
- MIT license with no subscription or seat feeCompositor is MIT licensed, which means you can download, run, modify, and redistribute it with no cost, no subscription, and no usage limits. Compared to Photoshop's subscription model and Affinity Photo 2's paid license, there is no ongoing financial commitment to keep using the full tool.
- Photoshop keyboard shortcuts and workflow parityCompositor ships with Photoshop-style keyboard shortcuts throughout, remappable in Edit > Keyboard Shortcuts, and replicates Photoshop-specific interaction patterns such as scrubbing a number's label to change its value. Existing Photoshop users can start working without relearning shortcuts or muscle memory.
- Native Apple silicon performanceBuilt in Swift for Apple silicon, Compositor runs GPU-accelerated layer effects and high-quality downsampling natively. It does not run through Rosetta translation, so it gets the full chip performance and battery efficiency of an M-series Mac.
- Open source and fully modifiableThe Xcode project is available to build, fork, and extend. A developer can add, remove, or change features directly in the Swift source rather than waiting for a paid vendor's roadmap. The app is signed and notarized and ships automatic updates.
Trade-offs
- -macOS 26 on Apple silicon onlyCompositor requires macOS 26.0 or later on a Mac with Apple silicon. It does not run on Intel Macs, older macOS versions, Windows, or Linux. Teams with mixed hardware or cross-platform workflows cannot use it as a shared standard.
- -New project with a short track recordThe repository was created in September 2026. The project is very early-stage with an unproven maintenance history. Features and the file format may change, and the issue tracker will likely surface gaps over time that a more mature tool would have addressed.
- -No CMYK support for PSD importPSD and PSB import supports 8-bit RGB only. CMYK Photoshop files are not supported. Print workflows that rely on CMYK color mode will need to convert files before they can be opened in Compositor.
Compositor vs alternatives#
Compositor vs Adobe Photoshop
Adobe Photoshop is the industry standard Compositor was built to replace for Mac users. The key differences are cost model and platform access.
| Feature | Compositor | Adobe Photoshop |
|---|---|---|
| License | MIT (free) | Proprietary |
| Price model | Free | Subscription |
| Platform | macOS 26+ on Apple silicon | macOS and Windows |
| CMYK support | No | Yes |
| PSD compatibility | Imports 8-bit RGB | Native format |
| Photoshop shortcuts | Yes (remappable) | Yes |
Compositor is the better choice for Apple silicon Mac users who want to stop paying a Photoshop subscription for compositing and post-processing work. Keyboard shortcuts carry over, the layer system replicates Photoshop's blend mode order, and PSD files open with editable layers. Adobe Photoshop remains the better choice for CMYK print work, Windows users, or anyone who needs features beyond compositing and post-processing, such as a video timeline, advanced type handling, or scripting with Photoshop Actions.
Compositor vs Affinity Photo 2
Affinity Photo 2 is a paid, proprietary image editor positioned as a Photoshop alternative on macOS, Windows, and iPad. Both tools target Photoshop users, but they differ on license, price, and platform coverage.
| Feature | Compositor | Affinity Photo 2 |
|---|---|---|
| License | MIT (free) | Proprietary |
| Price model | Free | One-time purchase |
| Source available | Yes | No |
| Platform | macOS 26+ on Apple silicon | macOS, Windows, iPad |
| CMYK support | No | Yes |
| AI-agent scripting | Yes (.comp format) | No |
Compositor is the better choice when zero licensing cost and source availability matter, or when you need AI-agent scriptability via the .comp project format. Affinity Photo 2 is the better choice for cross-platform teams that include Windows users, iPad workflows, or work requiring CMYK color mode.
Quick start#
Install Compositor via Homebrew or download the signed DMG from GitHub Releases.
```bash
brew install --cask robbietilton-compositor
```What it's built on#
- Languages
- CSwift
FAQ#
Is Compositor free to use?
Yes. Compositor is MIT licensed and available to download at no cost. There is no subscription, no free tier with paid features gated behind it, and no usage limit. You can use it for personal or commercial work without paying anything.
Does Compositor run on Intel Macs or Windows?
No. Compositor requires macOS 26.0 or later on a Mac with Apple silicon. Intel Macs and non-Apple platforms are not supported. If you need a cross-platform image editor, Compositor is not the right choice.
Can Compositor open Photoshop PSD files?
Yes, for 8-bit RGB PSD and PSB files. Folders, masks, blend modes, fill rectangles and ellipses, and simple horizontal text remain editable after import. CMYK files and complex vectors or vertical text are converted to pixels. A conversion report appears before any changes are applied.
What makes Compositor different from GIMP?
Compositor is built for Photoshop users who want familiar shortcuts and a workflow close to what they already know. It ships with Photoshop keyboard shortcuts remappable in Edit > Keyboard Shortcuts and replicates interaction patterns like label-scrubbing. GIMP uses its own interface conventions and workflow, which takes time to learn for anyone coming from Photoshop.
Can AI agents or scripts edit Compositor projects programmatically?
Yes. A .comp project is a folder of PNG layers and a manifest file. Any script or AI agent with file system access can write layers and update the manifest, and Compositor updates the open project live as files change. The format specification is documented at docs/writing-comp-files.md in the repository.
Similar open-source tools#
Pinta
Free open source image editor inspired by Paint.NET
Krita
Free open source digital painting app for artists
GIMP
Free image editor for graphic designers and photographers
MyPaint
Free open source painting app optimized for drawing tablets
Upscayl
Free open source AI image upscaler for Mac, Linux, and Windows
editor
Browser-based 3D building editor, MIT licensed and self-hostable