Free Online Video Voiceover Tool

Record voiceover narration over any video, at any timestamp, directly in your browser. No upload, no watermark, no account needed.

Supports MP4, WebM, and MOV. Your video never leaves your device.

How It Works

Upload your video

Drag and drop or select an MP4, WebM, or MOV file. Everything stays on your device.

Record voiceover

Scrub to any point in the timeline and record narration through your microphone. Add as many segments as you need.

Preview and download

Preview the mixed result in your browser, then download a polished MP4 with the new voiceover muxed in.

What You Can Use It For

Polishing process videos for SOPs

Record once, then add a clean voiceover where you fumbled or missed details. Drop the polished video into SOPX to turn it into a structured SOP.

Re-narrating screen recordings

Replace the on-the-fly narration in a tutorial or demo with a prepared script. No re-recording the screen.

Translating training videos

Keep the original screen capture, swap in narration in a different language. Faster than re-shooting in another language.

Adding context to silent footage

Have a video without commentary? Drop in voiceover at the moments that need explanation.

Why Use This Tool

Fully in your browser

No upload, no server, no account. Your video file never leaves your device.

Multiple voiceover segments

Record at one timestamp or many. Each segment is independent and easy to delete or re-record.

Original audio control

Keep the original audio in the gaps between voiceover segments, or replace the whole audio track.

Download as MP4

Get a clean MP4 file with the new audio muxed in, ready to share or upload.

Frequently Asked Questions

Find answers to common questions about SOPX.

What video formats are supported?

MP4 (H.264 and HEVC), MOV (QuickTime), and WebM. These cover the vast majority of screen recordings, phone videos, and meeting recordings.

Is my video uploaded to a server?

No. Everything runs in your browser. Your video file and microphone audio never leave your device.

What is the maximum video size and length?

1 GB or 20 minutes, whichever comes first. For best performance, use a desktop browser (Chrome or Edge) — large files may strain memory on mobile.

Can I record voiceover at multiple points in the video?

Yes. Scrub to any timestamp and record a voiceover segment. Add as many segments as you need. Recording is automatically blocked from overlapping an existing segment, so each moment in the timeline has at most one voice track.

Can I keep the original audio in parts where there is no voiceover?

Yes. A toggle lets you keep the original audio in the gaps between voiceover segments, or replace the entire audio track with voiceover only and silence elsewhere.

What output format will I get?

In Chrome and Edge, you get an MP4 file with the original video passed through and the new audio muxed in. In other browsers, the tool falls back to WebM output.

Polish process videos before they become SOPs

SOPX turns your process videos and screen recordings into structured, editable SOPs in minutes. Polish your video here, then let SOPX do the rest.

Try SOPX Free Book a 15-min demo