MediaMerger
Join several video clips into one MP4, entirely inside your browser. Nothing is uploaded. Back to the app
Quick start
- Drop two or more clips onto the page (or click Add videos). They are joined top to bottom.
- Reorder with the arrow buttons, or click a row and press
Alt+Up/Alt+Down.Deleteremoves the selected row. - Check the output name (it defaults to the first clip's name plus
_merged). - Click Quick Merge if it is enabled, otherwise Re-render.
Quick Merge vs Re-render
| Quick Merge | Re-render | |
|---|---|---|
| What it does | Copies the video and audio packets as they are and glues them together. | Decodes every frame, scales it onto one common canvas, and encodes a brand new H.264 file. |
| Speed | Seconds, even for large files. | Usually faster than real time on a PC with a graphics card, slower on phones. |
| Quality | Identical to the originals. | Re-encoded (choose High, Medium or Low). |
| Requirement | Every clip must match the first one exactly: same codec, size, frame rate, encoder settings and audio format. Typically clips from the same camera or the same export preset. | Anything the browser can decode. Different sizes are letterboxed to the largest clip. The frame rate is the highest one found (raising a rate duplicates frames and loses nothing). Clips without audio get silence so the sound stays in sync. |
The table marks clips that differ from the first one with a warning sign and the hint line says why. When any clip is marked, Quick Merge is disabled and Re-render is the way to go.
Where does the file go?
Loose files: the merged MP4 downloads to your Downloads folder. If you drop a whole folder, the browser asks once for permission and the merged file is written into that folder, never overwriting an existing file.
Supported input
mp4, mov, m4v, 3gp, mkv, webm with H.264, H.265, VP9 or AV1 video and AAC, Opus, MP3 or similar audio. Other containers (avi, wmv, flv, mpg, ts) are not supported here; use the desktop version for those.
Privacy
Everything runs in your browser using WebCodecs and a small WebAssembly module. No file or metadata is sent anywhere. It even works offline once loaded.
Browser
Chrome or Edge on Windows, Mac, Android and ChromeOS. Firefox and Safari lack the required WebCodecs encoder support.
Part of dirtsimple.app by the-Automator.com.