MediaSeg
ExaEdge · Video
MediaSeg is a free, local-first macOS utility that splits large video files into smaller, upload-ready chunks. It runs only on Apple Silicon Macs, handles MP4, MOV, and WEBM, and keeps your files on your machine from start to finish. If you've ever tried to feed a long recording into a tool that caps uploads at 200MB, this is the video splitter app built for exactly that problem.
About MediaSeg
What Is MediaSeg
MediaSeg is a media splitter for macOS that cuts long recordings into pieces small enough to upload to size-limited platforms. Meeting captures, lectures, webinars, and long screen recordings often run past the file size limits that many web tools enforce, and MediaSeg handles that job locally.
The main trick is how it treats MP4. So what makes that different from just using a video editor? Instead of re-encoding your video, MediaSeg works as an MP4 file splitter that uses a stream-copy path, so the output chunks keep the original quality and split fast. WEBM gets converted to MP4 first, then split. It's a single-purpose utility, not an editor, and that's the point.
The clearest limits are the platform and the hardware. MediaSeg is macOS only, and it needs an Apple Silicon Mac running macOS 15 Sequoia or later. Windows and Intel Mac users are out of luck here. There's also no API, so you can't wire it into an automated pipeline.
Getting Started
- Download the latest release from the MediaSeg GitHub page and drag the app into your Applications folder. Release builds bundle FFmpeg and FFprobe, so there's nothing else to install.
- Launch MediaSeg and open the input file through the app, or run it from the command line with
python3 mediaseg.py "/path/to/video.mp4". - Set your target chunk size. The default is 200MB, and you can change it to match whatever upload limit you're dealing with.
- Start the split and let it run. MediaSeg writes sequential files into a timestamped output folder, like
TrainingVideo_001.mp4,TrainingVideo_002.mp4, and so on. - Upload the chunks to your target platform, then delete the folder when you're done.
Product Information
A quick look at MediaSeg's pricing, supported platforms, and performance.
Best for
The users, tasks, and scenarios where this tool fits best.
Users
- Students and researchers uploading long lectures
- Meeting and webinar organizers
- Anyone with large local media
Tasks
- Splitting long MP4 recordings
- Converting and splitting WEBM
- Joint-size-limited uploads
- Handling audio-only files
Scenarios
- Prep work before uploading to a size-capped AI tool
- Archiving a long screen recording into digestible parts
- Offline or privacy-sensitive workflows
Key features
Local-only processing
Every split happens on your Mac. MediaSeg never uploads your source file, which matters when the footage is confidential or just large enough that uploading it twice feels wasteful. The trade-off? All the work runs on your machine, so speed depends on your hardware. Big files still take time.
No-re-encode MP4 splitting
MediaSeg splits MP4 with a stream copy, meaning it moves the existing video and audio streams into new files rather than decoding and re-encoding them. Quality stays exactly as it was, and the split finishes in a fraction of the time a full re-encode would take given that a typical long recording can carry many gigabytes of encoded frames that a normal editor would have to decode, process, and write back from scratch. This is the feature that makes the app worth using over a general-purpose video editor.
Configurable chunk size
You set the target size, and MediaSeg treats it as a hard upper bound, aiming for roughly 90% to 98% of the limit when it can. If you're sticking to the 200MB default, the output lands just under that. Change it once and the app respects it for every split. Simple.
Broad format support
MP4, WEBM, and MOV are officially supported, with M4A, MP3, and WAV available as experimental. Output keeps sensible extensions, so MOV becomes MOV and audio files stay in their original format. The experimental label is an honest warning. Those formats get less testing.
Theme and language options
The GUI ships with System, Dark, Light, and Neon Tokyo themes, plus English, Japanese, and Vietnamese language support. It's a small touch, but the Neon Tokyo theme has a following. GUI polish landed in v1.2.0 alongside cleaner processing overlays.
Bundled FFmpeg and FFprobe
Release builds include FFmpeg and FFprobe under the LGPL, so you don't have to install them yourself. Source runs still need a local ffmpeg install, and the GUI warns you when a dependency is missing. Most users should just grab the release build. Skip the setup.
Pros and cons
Pros
- Free and open source, with release builds that bundle FFmpeg so there's no dependency hunting.
- The MP4 stream-copy path splits without re-encoding, which preserves quality and saves time.
- Local processing keeps large or sensitive files off external servers.
- Configurable chunk size lets you match any upload limit, not just the 200MB default.
- Active development: three releases shipped within a week of launch.
Cons
- macOS on Apple Silicon only, so Windows, Linux, and Intel Mac users can't run it at all.
- No API, which rules out automated or scripted splitting pipelines.
- Audio formats like M4A, MP3, and WAV are still experimental and less tested than the video paths.
- WEBM input gets converted to MP4 before splitting, so the output format changes.
Frequently asked questions
MediaSeg splits large media files into smaller chunks that fit upload size limits. It's aimed at long recordings that a platform like NotebookLM would otherwise reject for being too big. You point it at a file, set a size, and it produces numbered pieces.
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