Add Audio to Video Online

Add music or a voice recording, replace original sound, or combine separate video and audio files. Set each volume manually and export an MP4 locally in your browser.

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Your video stays on your device — processed locally in your browser, never uploaded.

Quick Facts About Add Audio to Video Online

Add music or a voice recording, replace original sound, or combine separate video and audio files. Set each volume manually and export an MP4 locally in your browser.

Inputs: One supported local video and one supported audio or media file
Output: MP4 with re-encoded H.264 video and AAC audio, or Opus fallback
Volume controls: Original and added audio: 0–200% independently; original audio can be muted
Audio timing: Added audio starts at the beginning; no adjustable start offset
Audio behavior: One stereo mix; manual balance, with no automatic ducking
Processing: Local decoding, mixing and re-encoding; no source upload
Practical limits: Codec support and available memory; preview and check the complete export

Add Audio vs Replace Audio vs Merge Separate Tracks

Choose the workflow by deciding whether the original sound should remain audible. These are different uses of the same two-source mixer, rather than separate export modes. Both volume settings are constant for the export: TakeVid does not automatically lower music when speech begins, and it does not record a voiceover for you. Load a voice recording as the added audio file.

Goal	Original audio	Added audio
Add background music	Keep at a suitable volume	Lower the music volume manually
Add a voiceover	Keep, lower or mute it manually	Load a recorded voice track
Replace original sound	Mute the original	Use the new track as the soundtrack
Merge separate video and audio	Choose the video-only file	Choose its matching audio file
Give a silent clip a soundtrack	No original track is needed	Load the desired audio file

Downloaded Video and Audio Separately?

Some media is delivered as independent video and audio tracks. If you have permission to edit the downloaded files, select the video-only file in the video input and its matching audio file in the added-audio input. An MP4 video with an MP3 or M4A soundtrack can be a suitable combination when the browser can decode those particular files. A filename extension alone does not establish codec compatibility. The tool combines one video with one added audio track; it does not fetch missing tracks from a website or automatically synchronize unrelated recordings. Added audio starts at the beginning, so use matching tracks or prepare the timing first.

Adding Music Re-encodes the Video and Sound

TakeVid decodes the video frames and exports H.264 in an MP4 container. It mixes the decoded audio samples and encodes a new stereo soundtrack, normally as AAC; the audio helper can fall back to Opus when AAC encoding is unavailable. This is different from remuxing, which copies compatible compressed tracks without decoding. Re-encoding can change quality and file size, and MP4 with Opus is less broadly supported than MP4 with AAC. Check the exported file in the player or device where it will be used.

Balance Audio Manually and Check Track Lengths

Start with moderate levels and lower music until speech is clear. Raising both tracks can clip peaks; the mixer caps sample values rather than applying a mastering limiter or automatic ducking. Check that the added audio covers the section you want to hear, and review both the beginning and the end of the result. For a silent video, use an audio file prepared to the required duration and turn looping off when it is unnecessary. A loop control is available, but it should not be treated as a guarantee of seamless timing for every input combination.

How to Add Audio to a Video

Select a supported video and one readable music, voice or matching audio file.
Keep, lower or mute the original sound and set the added-audio volume. Check the track lengths before exporting.
Process locally and review the beginning, end and sound levels of the MP4 before downloading.

Why Use TakeVid to Add Audio to Video

Independent original and added-audio volume settings from 0% to 200%
Mute original sound to replace the soundtrack
Keep both tracks audible for voice plus background music
Combine one video-only file with its matching audio file
Added audio begins at the start; no automatic alignment or speech ducking
Loop control for short audio; check timing in the completed export
H.264 MP4 with newly encoded sound; AAC where supported, otherwise an Opus fallback
Runs locally with WebCodecs — files are not uploaded
Free, with no registration or added watermark

Supported Video and Audio Formats

Supported MP4, MOV, WebM or MKV video and readable MP3, WAV, M4A/AAC, OGG, FLAC or an audio track from another supported file. Codec support differs between browsers and processing paths. Output is H.264 MP4 with AAC audio where available or Opus as a fallback; test playback in the destination app.

Common Use Cases

Combine separately downloaded video-only and audio-only files into one video
Score a vlog, travel or lifestyle video with your favorite track
Add a voiceover while keeping the original sound audible underneath
Mute noisy or wind-blasted footage and replace it with a clean soundtrack
Add a branded soundtrack to product demos and promotional clips
Give silent screen recordings and tutorials a music bed
Loop a short jingle across the whole video without editing software

Privacy & Browser Processing

This tool runs entirely in your browser using WebCodecs. Your video is decoded, processed and re-encoded on your device — it is never uploaded to a server, and everything is released when you close the tab.

Download Videos with TakeVid

TakeVid is a browser extension that detects supported video and streaming resources on many websites. Save compatible media in your browser, then edit the source clip with these local video tools.

Install TakeVid Extension

Frequently Asked Questions

Can I merge a separate audio file with a video?

Yes, when the files and codecs are readable. Choose the video-only file and its matching audio track. Added audio starts at the beginning; the tool does not automatically synchronize unrelated recordings.

Can I add background music without removing the original audio?

Yes. Keep the original audio enabled and lower the added-audio volume until speech is clear. Levels are constant; there is no automatic ducking when someone speaks.

Can I replace the original audio?

Yes. Set the original video's volume to zero or mute it, then use the added audio as the output soundtrack — useful for noisy or wind-blasted footage.

What happens if the audio is shorter than the video?

A loop control is offered, but review its result with your files. For a silent video, prepare an audio track covering the desired duration and turn looping off when unnecessary. With looping off, the portion after the added track ends has no added sound.

What happens if the audio is longer?

The added audio is trimmed at the video's end automatically — no manual cutting needed.

Can I merge MP4 and M4A?

A video-only MP4 and matching M4A can work when the browser can decode them. Other supported audio inputs include MP3, WAV, OGG and FLAC; the extension alone does not guarantee compatibility.

Will the picture quality change?

Video is re-encoded as H.264 and the sound is mixed and re-encoded. Quality and size can change. AAC is used where supported, with an Opus fallback; check playback on the destination device.

Will my files be uploaded?

Your selected files are processed on your device and are not uploaded to TakeVid. The page and processing modules must load first; available browser codecs and memory still limit what can be processed.