Files stay private
Processing runs on your device. No media upload or server processing queue.
Merge Video and Audio Online
Bring your video and soundtrack together in one file. Merge locally in your browser, keep the original video quality, and download without uploading or signing in.
01
Your video
▸Drop a video here
MP4 · MOV · WebM · MKV · AVIThis browser cannot preview the file. You can still try merging it locally.
02
Your audio
♪Drop an audio file here
MP3 · M4A · AAC · WAV · FLAC · OGGThis browser cannot preview the file. You can still try merging it locally.
Up to 2 GB combined · one video + one audio file
Loading the local merge engine
0%
✓Merged on your device
Your video and audio, together
Browser previews depend on the output format and codecs. If playback is unavailable or silent, download the file and check it in a compatible player.
File size—
Format—
Quality—
!
Unable to merge these files
Selected files—
MP4 output · original video and audio quality · both tracks kept in full
♪
The selected audio replaces the video’s original sound. This tool does not mix the two soundtracks.
▣Your files stay on your device. Audio and video are processed in this browser, never uploaded.
The picture you made. The sound you chose.
Pair a silent clip with music, reunite separately saved tracks, or replace a recording’s soundtrack. Choose a video and an audio file, then package them together on your device.
Video track
+ Audio track
→ Merge locally
→ One download
The encoded video and audio tracks are copied into one MP4 file without re-encoding. Your video keeps its original resolution, frame rate and picture quality.
How to merge video and audio
- 1
Choose two files
Select your video and audio, or drop them into their separate areas.
- 2
Check your files
The output is MP4; both tracks are copied without re-encoding and kept in full.
- 3
Merge and download
Let your browser combine the tracks, then save the finished file.
A simple way to finish your video
Give your video its soundtrack
Keep your picture
The video is copied without re-encoding, preserving its resolution and encoded frames.
Ready to save
Download one MP4 containing your selected video and audio tracks.
Music for silent clips
Pair a silent video with a music track you have chosen.
Separate recordings
Combine matching video and audio files saved separately.
Narration and voiceovers
Attach a finished narration track to an explainer or screen recording.
Frequently Asked Questions
Are my files uploaded?
No. Your browser reads and merges the files locally. It downloads the processing engine, but does not send your video or audio to a processing server.
Does merging reduce video quality?
No. The original video and selected audio tracks are copied without re-encoding.
What happens to the original sound?
It is replaced by the first audio track from the audio file you select. Original audio, subtitles and other extra tracks are not included.
What if the audio and video have different lengths?
Both tracks start together and are kept in full. The shorter one ends first; audio is not repeated or padded.
Why might lossless MP4 merging fail?
The original video or audio codec may not be supported by MP4 or this engine. Use compatible source files or convert them separately first.
Can I use this on a phone?
A browser with WebAssembly and Web Workers can run the tool. Large files can exceed a phone’s memory, so smaller files are more suitable.