Sometimes you just want to merge some clips, not open Final Cut
You’ve got a handful of clips from a trip or an event and you just want them stitched into one file, stabilized, and with the volume evened out. Firing up Final Cut Pro or Premiere for that feels like overkill. That frustration is exactly why I built MP4 Merger, a small native macOS app, and I’m giving it away for free on GitHub.
Here’s what it does and how to use it.
What MP4 Merger does
Drop your video files in, and it can handle all of the following in one pass:
- Merge or batch-process: combine multiple clips into a single file, or apply the same processing to each file individually.
- Automatic volume normalization: analyzes inconsistent audio levels across clips and evens them out to a comfortable, consistent level.
- Gimbal-style stabilization (two-pass): smooths out handheld camera shake using a two-stage stabilization process.
- Resolution scaling: output at 1080p FHD or 4K UHD.
- Jitter correction: reduces subtle playback stutter for smoother viewing.
It’s fully optimized for Apple Silicon (M1/M2/M3), using native VideoToolbox hardware acceleration — encoding finishes at several times realtime speed. HEVC output is supported too, so you keep quality while saving disk space.
Using it is dead simple
- Drag and drop your video files into the dashed area in the middle of the window.
- In the Options panel, choose “merge” or “process individually,” and toggle audio normalization, stabilization, or your target resolution as needed.
- Hit the blue “Merge Files” button and you’re done.
The UI is a native dark-mode Mac app — it feels like it belongs on your system, not like a cross-platform wrapper.
Small details that took way more effort than they look like
The interface looks simple, but a lot of the actual engineering effort went into the small stuff that makes it feel good to use.
- Fast when it can be, and honest when it can’t: if the clips you’re merging already share the same codec/resolution/etc., MP4 Merger can stitch them together without re-encoding at all, so it finishes almost instantly. When a re-encode is unavoidable, it asks first — “this will take a while, continue?” — instead of silently making you wait.
- No need to click Clear: if you still have a previous batch loaded and drag in a new set of files, the app automatically clears the old list before loading the new one. One less button to remember.
- Your original files are never touched: every operation — merging, upscaling, stabilization — writes to a new output file. The source files you dragged in are never modified. Even if a merge or upscale fails midway, your originals are completely safe.
- Finder tags carry over: any Finder tags you’d already applied to the source videos for organization are preserved on the new output file after merging, upscaling, or any other processing — no need to re-tag anything afterward.
Despite the name, it’s not just for merging
“Merger” is right there in the name, but you don’t need multiple files to use it. Load a single video and choose “process individually,” and you can apply just the upscaling or the shake/jitter correction to that one clip — no merging required. If all you want is to steady a single shaky video, that works too.
Installing it
The distributed zip is signed and notarized by Apple, so you can download it from GitHub Releases and just run it — no “unidentified developer” warning.
The video engine, FFmpeg, isn’t bundled inside the app. On first launch, a setup screen walks you through either installing it via Homebrew or downloading an official build from evermeet.cx (with SHA-256 verification built in). If FFmpeg is already installed, the app just finds it automatically.
(This design choice is deliberate: the standard FFmpeg builds people install include GPLv3-licensed components. Rather than bundle — and effectively redistribute — a GPL binary myself, the app stays MIT-licensed and lets you fetch FFmpeg yourself, which keeps the licensing story simple and clean.)
- Download: GitHub Releases – MP4 Merger
- Source: github.com/yamachan03/MP4Merger
- License: MIT (see the FFmpeg note above for the video engine itself)
Who this is for
- Anyone who just wants to merge a pile of video clips into one file, fast.
- Anyone with shaky handheld footage who wants a quick fix.
- Anyone who wants light video cleanup without opening a full editing suite.
The full source is on GitHub. If you find it useful, a star is always appreciated — and bug reports or feature requests are welcome via Issues.
(Screenshot to be added here)
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