What it does
Subler is a macOS application for muxing and tagging MP4 files. It accepts supported tracks from MOV, MP4, MKV, and selected elementary formats.
Use Subler when the existing streams need to be assembled into an MP4 with the right captions, chapters, and metadata. Its subtitle outputs include TX3G and WebVTT for compatible playback environments. This track-oriented workflow is distinct from choosing a new video encoder; verify that the source streams and target player support the intended combination.
The download requires macOS 10.13 or later. For files expected to exceed 4GB, the FAQ calls for 64 Bit chunk offset; it is off by default because some older devices cannot read that MP4 layout. Optimize interleaves audio/video and moves the movie metadata to the beginning for fast start. SRT import can depend on text encoding, with UTF-8 recommended when detection fails. Metadata lookup uses external services, while the core task is assembling compatible tracks into a local MP4. The official source repository includes GPL version 2 licensing.
Strengths
- Focuses on MP4 track assembly, captions, chapters, and tagging.
Best for
- Preparing tagged MP4 files from compatible media tracks
Sources
- Subler (Oct 26, 2026)
- FAQ · SublerApp/Subler Wiki · GitHub (Oct 26, 2026)
- Subler/COPYING at main · SublerApp/Subler · GitHub (Oct 26, 2026)