Drag and drop your video here
or click to browse
Supported: MP4, WebM, MOV, MKV
Max file size: 2 GB
Drag and drop audio here
or click to browse
Supported: MP3, WAV, M4A, AAC, OGG, FLAC
Max file size: 500 MB
Loudness of the added audio in the final mix.
When the added audio begins on the video timeline.
When the added audio stops on the video timeline.
Disable to silence the source video soundtrack.
Scale the final mix so the loudest peak sits below clipping.
Repeat the added audio to fill the selected range.
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Your processed video will appear here after you add audio and click the button.
Files selected from your device are processed locally in your browser. We never upload or store your video or audio.
Add Audio to Video lets you attach a music track, voice-over, or sound effect to any clip directly in your browser. Upload the video, drop in the audio, set volume and fades, and export a finished MP4 with no installs and no upload.
The tool decodes both files in your browser, mixes the original soundtrack with the added audio according to your settings, then re-encodes a new MP4 with the combined audio baked in.
Creators publishing to social platforms, marketers preparing product clips, teachers and trainers adding narration, podcasters cutting promo videos, and developers reviewing screen recordings can all benefit.
Reach for it when you need to layer background music, replace a noisy original audio track, add voice narration, or insert a short sound effect on top of an existing recording.
Local files never leave your device. URL mode only fetches the source from its origin server through your browser; nothing is mirrored or stored on appkiro.
Upload is best for private files. URL is for direct public links. Streaming pages, sign-in walls, and signed CDN links usually block browser access.
Controls how loud the added audio is in the final mix relative to its original loudness. 100% keeps the audio at full strength, 50% reduces it to half, and so on.
The added audio ramps from silent to full volume over this many seconds at the start. Useful for music that should ease in instead of starting abruptly.
The added audio ramps from full volume to silent over this many seconds at the end. Pairs well with fade-in for clean intros and outros.
Define the precise window on the video timeline where the added audio plays. Use HH:MM:SS.mmm or seconds. Anything outside the window is silent for the added track.
Add as background mixes both tracks together. Replace original drops the source soundtrack so only the added audio plays. Voice-over ducks the original to about 30% so narration sits on top.
Master switch for the source soundtrack. Turn it off to silence the original entirely regardless of the position setting.
Scans the final mix for the loudest peak and scales the entire track so the peak sits just below clipping. Helps balance loudness when mixing music with quieter dialogue.
If the added audio is shorter than the selected range, it repeats seamlessly until the range is filled. Ideal for short ambient loops.
No. Local video and audio are decoded, mixed, and re-encoded entirely in your browser. URL mode only fetches the file from its original server.
Video: MP4, WebM, MOV, MKV. Audio: MP3, WAV, M4A, AAC, OGG, Opus, FLAC. The browser must be able to decode the codec used inside the file.
The result is an MP4 file with H.264 video and AAC audio when your browser supports them, falling back to the first encodable codec available.
Background mixes the added audio with the original at full volume. Replace silences the original entirely. Voice-over keeps the original at about 30% volume so the added track sits clearly on top.
When the added audio is shorter than the selected range, the same audio loops seamlessly until the range is filled. It is useful for short background music or ambient loops.
Normalization scans the final mix and scales the loudest peak to a safe level (about -0.5 dBFS) so the output is loud enough without clipping.
Yes. Set Start time and End time under Audio Settings. Only the selected portion is mixed into the video and the rest is discarded.
The video timeline is the source of truth. If the added audio is longer than the video, anything past the video duration is cut. If shorter, it stops naturally or loops when looping is enabled.
The video is re-encoded so the new audio can be muxed into a clean MP4. Quality is preserved as much as the browser encoder allows; lower-resolution sources stay close to their original sharpness.
Remote sources must be a direct media URL that allows browser CORS plus Range requests. Streaming pages, signed-only CDNs, and download portals usually do not.
No. Both source files remain untouched. The tool produces a brand new MP4 you download separately.
Browser memory and codec support are the practical limits. Smaller files, common MP4 sources, and updated browsers (Chrome, Edge, Safari, Firefox) work most reliably.