MP4Joiner vs Avidemux: Two Free Ways to Join MP4 Files
Avidemux and MP4Joiner are the two free, open-source tools that can join MP4 files without re-encoding — and they could hardly feel more different. Avidemux is a general video editor whose Append function, combined with Copy mode, can stitch files together. MP4Joiner is a single-purpose tool: a list of clips, an order, one Join button. Neither costs anything, so this comparison is purely about fit.
How each one joins
Avidemux: open the first file, use File → Append for each additional file, set video and audio output to Copy, choose the MP4 muxer, and save. If the clips share the same encoding parameters, the streams are copied — lossless, like MP4Joiner. If they don’t, Copy mode can produce broken or out-of-sync output, and Avidemux’s warnings about mismatched streams are easy to miss. You can also mark sections with the A/B markers and delete or export segments, which makes it a capable basic trimmer.
MP4Joiner: drag clips into the list, reorder them with the arrow buttons, and click Join. The same parameter rule applies — matching clips copy losslessly — but the workflow is built for exactly this job, and a force re-encode option is offered in the open when parameters differ, instead of failing quietly. The same installer also provides MP4Splitter for the reverse job of splitting a file into parts.
Side by side
| Dimension | Avidemux | MP4Joiner (MP4Tools 3.8) |
|---|---|---|
| Type | General free video editor | Dedicated free joiner (+ MP4Splitter) |
| Lossless joining | Yes, via Append + Copy mode, when parameters match | Yes, by default, when parameters match |
| Mismatched clips | Copy mode may misbehave; the alternative is a full manual re-encode setup | A clearly labelled force re-encode option handles it |
| Batch joining | Weak: one append chain at a time, assembled by hand | The clip list is the batch; reordering is built in |
| Trimming | A/B markers, delete or save segments — its strength | A simple built-in cut function |
| Splitting | Indirect: export segments one at a time | MP4Splitter is included for exactly this, with a keyframe option |
| Formats | Many input formats and containers | MP4-family only (plus audio joining) |
| Learning curve | Dated interface; editor concepts (muxers, copy vs encode) to learn | Minimal: add, order, join |
| Platforms | Windows, macOS, Linux | Windows and macOS; Linux from source |
| Price | Free and open source | Free and open source (GNU GPL) |
The verdict
Reach for Avidemux when joining is occasional and trimming is frequent, or when your files are not MP4 to begin with — its editor DNA gives it broader format support and real segment editing. It is available from the Avidemux project site.
Reach for MP4Joiner when joining is the recurring job: a purpose-built list, honest handling of mismatched clips, and a splitter in the same package. Download it here and follow the step-by-step guide.
Bottom line: two free tools, two shapes. Editor-with-append versus dedicated joiner — pick by which task you repeat.
The wider field, including paid options for when free tools run out of road, is in our best MP4 joiners roundup. Joining questions are answered in the FAQ. This page contains no affiliate links. See our affiliate disclosure.