# Replace Video Audio - Loop & Volume Keep video length, loop or pad audio, and set volume - distinct from shortest-only mux tools ### Video, Audio & Options Video file MP4 / WebM / MOV Audio file MP3 / WAV / M4A Keep full video length Loop audio to cover video Volume (1.00×) _1_ Replace Audio Clear Unlike Add Music (shortest), this keeps picture length by default · local browser processing · Max ~100 MB each ### Preview Result appears here ## What is Replace Video Audio? Replace Video Audio swaps a clip’s soundtrack while keeping picture length by default. Unlike a simple shortest mux, it can loop a short bed, pad silence to the end, and adjust volume-then export MP4 in your browser. Creators use it when a licensed track must cover the full edit, when narration is shorter than the picture, or when a temp bed needs a volume trim without opening a DAW. It is related to Add Music to Video but aimed at length-faithful delivery. Choose Add Music for quick shortest muxes; choose Replace Audio when the video timeline is sacred. Everything stays local with local browser processing. Client films and unreleased cues never need a cloud muxer. Preview loudness carefully. Volume is a multiplier, not a loudness normalizer with true peak limiting. Small media chores still burn calendar time when every task means a new desktop project. (note 1). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Working inside a browser memory budget nudges you toward shareable source sizes from the start. (note 2). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Visible status lines prevent the false assumption that a tab froze during a long encode. (note 3). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Resetting the form between exports stops stale previews and wrong filenames from sneaking through. (note 4). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Chaining ToolComb video pages creates a private pipeline without creating yet another SaaS account. (note 5). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Spot-checking on phone and laptop screens reveals soft text and pacing issues early. (note 6). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Naming downloads with clear suffixes makes it easier to find the latest take in a busy folder. (note 7). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Prefer the simplest setting that meets the requirement; extra knobs often invite accidental quality loss. (note 8). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. If a job fails, shrink the source or simplify options before assuming the browser is broken. (note 9). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Document the settings you used when a result looks perfect so the next episode matches. (note 10). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Small media chores still burn calendar time when every task means a new desktop project. (note 11). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Working inside a browser memory budget nudges you toward shareable source sizes from the start. (note 12). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Visible status lines prevent the false assumption that a tab froze during a long encode. (note 13). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Resetting the form between exports stops stale previews and wrong filenames from sneaking through. (note 14). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Chaining ToolComb video pages creates a private pipeline without creating yet another SaaS account. (note 15). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Spot-checking on phone and laptop screens reveals soft text and pacing issues early. (note 16). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. Naming downloads with clear suffixes makes it easier to find the latest take in a busy folder. (note 17). When you use replacing video audio on ToolComb, stay in a short loop: load media locally, change only the settings that matter, follow the local browser processing status log, preview the output, and download once you are happy. That habit replaces installing a full editor for a single chore and keeps confidential footage off anonymous cloud converters. ## How to replace a video soundtrack Upload video and audio, pick length behavior, set volume, export. 1. **Upload video** Picture length is kept by default. 2. **Upload audio** MP3/WAV/M4A you may use. 3. **Set options** Keep length, optional loop, volume. 4. **Replace** Start the export to replace the video’s existing sound. 5. **Preview and download** Check loudness, then save the MP4. ## Example: looping a 20s bed under a 90s demo ### Before A marketer has demo.mp4 (90s) and bed.mp3 (20s). Shortest mux would cut the video at 20s. ### After They enable keep length + loop audio at volume 0.8 and export a full 90s MP4. If the bed feels busy, they drop volume to 0.5 and re-run without reopening an editor. ## Ten uses for length-aware audio replace ### 1. Full-length music beds Cover the entire picture with a loop. ### 2. Narration shorter than video Pad silence to the end. ### 3. Temp to final swap Drop in the licensed cue late. ### 4. Volume matching Nudge loudness without a DAW. ### 5. Silent screen demos Add a calm bed under UI captures. ### 6. Multilingual VO Swap language tracks per market. ### 7. Podcast video Attach cleaned audio masters. ### 8. Event recaps Replace noisy venue sound. ### 9. Ad variants Same picture, different music stings. ### 10. Privacy Remove original room audio entirely. ## Replace Audio vs Add Music vs editors Similar mux jobs differ in duration rules and controls. | Consideration | Replace Audio | Add Music to Video | Desktop editor | | --- | --- | --- | --- | | Default duration | Keep video length | Shortest wins | Timeline | | Loop audio | Yes | No | Yes | | Volume | Multiplier | None | Full mixer | | Best for | Length-faithful swaps | Quick shortest mux | Complex mixes | Pick the smallest tool that preserves the length and loudness rules you need. ## Limitations to keep in mind - No ducking or multi-track mix. - Volume is linear, not LUFS targeting. - Loop may create abrupt seams at bed boundaries. - Each upload can be about 100 MB because the job runs in browser memory. - The first run downloads and compiles the local browser processing engine, so it is slower than later runs. - Unusual codecs may not be readable by the browser build of local browser processing. - Very long or very high-resolution clips can be slow or fail on devices with limited RAM, especially phones. - If you close or reload the tab while processing, the job stops and must be restarted. ## Privacy and good practice Your files are read by the Replace Video Audio page and written into a temporary in-memory file system used by local browser processing. Processing happens on your device. Media is not uploaded to an encoding server. The only network fetches are the page itself and, on first use, the generic local browser processing engine files of roughly 25 MB. Those files do not contain your video. Closing the tab discards temporary data. Downloaded results land in your normal downloads folder. On a shared computer, delete them when finished and empty the recycle bin if the material is sensitive. ## Frequently Asked Questions ### How is this different from Add Music to Video? Add Music uses shortest duration and ends when either stream ends. Replace Audio keeps video length by default, can loop short audio, pad with silence, and offers a volume multiplier-better when the picture length must stay intact. ### What does keep video length do? When enabled, output matches the video duration. Shorter audio is padded (or looped if that option is on); longer audio is trimmed to the picture. ### What does loop audio do? It repeats the soundtrack until the video ends-useful for short beds under longer clips. ### How does volume work? A linear multiplier: 1 is unchanged, 0.5 is quieter, 1.5 is louder. Extreme values can clip; preview before sharing. ### Is original audio mixed in? No. The new track replaces the old one. Mix offline if you need both. ### Are files uploaded? No. The files are processed in your browser. ### Formats? Video: MP4/WebM/MOV… Audio: MP3/WAV/M4A… Output MP4 with AAC. ### Picture quality? Check the downloaded result before publishing. Keep the original video if it is your archive master. ### Rights? You must be allowed to use the replacement audio on your platforms. ### Size limit? About 100 MB per file. ## Related video tools - [Video trimmer](https://www.toolcomb.com/video-trimmer) - Cut by start/end time. - [Video compressor](https://www.toolcomb.com/video-compressor) - Shrink with CRF or bitrate. - [Video to GIF](https://www.toolcomb.com/video-to-gif) - Export an animated GIF. - [Video to MP3](https://www.toolcomb.com/video-to-mp3) - Extract soundtrack as MP3. ## Related Tools Discover more free tools that might help with your next task. [Add Music to Photo Still photo + soundtrack → MP4 video Use Tool](https://www.toolcomb.com/music-to-photo) [Remove Audio from Video Mute a video / strip the soundtrack Use Tool](https://www.toolcomb.com/remove-audio-from-video) [Add Music to Video Replace a video soundtrack with your music Use Tool](https://www.toolcomb.com/add-music-to-video) [Audio Trimmer Cut MP3/WAV clips by start and end time in the browser Use Tool](https://www.toolcomb.com/audio-trimmer) [Audio Joiner Merge multiple audio files into one track Use Tool](https://www.toolcomb.com/audio-joiner) [Audio Converter Convert between MP3, WAV, OGG, and M4A locally Use Tool](https://www.toolcomb.com/audio-converter) ### Related guides Read the how-to, then come back to this tool when you are ready to run it locally. - [Mute and Replace Audio Track Safely (Browser) Swap narration, add licensed music, or strip room tone with FFmpeg.wasm locally. Sync, ~100 MB per file, first-load engine, and copyright you still owe.](https://www.toolcomb.com/blog/mute-replace-audio-track-safely) - [Best Free Browser Audio and Video Tools (FFmpeg.wasm) Trim, join, compress, GIF, MP3, subtitles, and waveform exports without uploading media. How ToolComb's FFmpeg.wasm tools map to real chores - and where ~100 MB and first-load limits apply.](https://www.toolcomb.com/blog/best-free-browser-audio-and-video-tools) [View All Tools](https://www.toolcomb.com/tools)