Concat is pitched as a free CapCut replacement, and its listed features include auto-captions, text-to-speech, background removal, keyframes, multi-track cutting, 4K export. For developers, the more important line is further down. Concat ships an MCP server built in, so an AI agent can edit video with it, plus a JSON-RPC API for scripts. A video editor that an agent can drive, running entirely on your own disk, is a different tool from a consumer app with an AI button.
The README describes Concat as an open-source editor for macOS, Windows, Linux and Android, with iPhone and iPad builds that are sideloaded. Everything runs on a native Rust engine with a GPU compositor. It is licensed AGPL-3.0 and, in its own words, in beta: it works, and it still has edges.
Local by design
The README's "none of the catches" list is short: no watermark, no account, no subscription, no upload. The AI pieces follow the same rule. Captions use local Whisper, where you pick a model size and get styled captions on the timeline. Voices come from free local text-to-speech, or from voice cloning based on a few seconds of a recording. Background removal handles people and objects, or you paint the mask yourself. The README says these models download once from Settings and then work offline, and that your footage never leaves your disk.
If I were editing client footage, interviews or internal recordings, that last point would matter to me more than the effect count. There is a CODE_SIGNING.md that the README says explains why Windows builds are not signed yet and what Concat sends over the network, which it summarizes as nothing you did not ask for. That document is worth a read before installing an unsigned build on a work machine.
The machine interface
The README lists three ways to drive Concat without the mouse:
- An MCP server started with
concat --mcp, with setup indocs/MCP.md. The README calls it one line to set up and names Claude among the agents that can edit with it. - A JSON-RPC API for scripts.
- gRPC and a command-line tool, which the README says a build from source adds.
The developer docs on the project website cover the Concat API and its transports. The README does not list the individual MCP tools or RPC methods, so it does not show how fine-grained the control is, for example whether an agent can place a keyframe or only run whole operations. That is the first thing I would check in the docs before planning an automated pipeline around it.
The README's "Good for" list includes Shorts, Reels, tutorials, screen recordings and podcast clips. Topics on the repository include video-editing automation and YouTube automation.
The voice cloning question
Voice cloning from a few seconds of a recording is a capability worth pausing on. The README presents it as a feature alongside free local voices, and it does not describe consent checks or restrictions. If your team adopts Concat, decide up front whose voices you will clone and get permission in writing. The README does not mention consent checks of any kind.
Getting it running
The README gives two download routes: the project website, which hands you the right build, and GitHub Releases with installers, packages and checksums for every platform. Windows is x86_64 only for now, with ARM builds paused. If SmartScreen blocks the unsigned build, the README says to choose More info and then Run anyway. On macOS it gives an xattr -dr com.apple.quarantine command for an unsigned app. Linux gets .deb, .rpm, AppImage, an Arch package and a community Flatpak.
Building from source needs Rust 1.93 or newer, FFmpeg 7 or newer development libraries, cmake and a C++ compiler, then cargo run -p concat from the src directory. CI runs cargo fmt --check and cargo clippy with warnings denied.
The project's advice to contributors is to grab a release, use it, and find where it breaks. I would apply the same advice to an evaluation. For a team weighing it, I would cut one real video by hand first, then try the same edit through MCP and see how much of it the agent can actually do.
GitHub: https://github.com/jub0t/Concat
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