Online Video Merger

Online Video Merger — Combine Multiple Videos Into One

Online Video Merger is a free, browser-based tool that lets you join multiple video files into a single video in any order you choose. All processing happens locally in your browser — no files are uploaded to any server, keeping your content completely private.

Key Features

• Wide Format Support: Works with MP4, MOV, AVI, MKV, WebM, FLV, WMV, TS, and more. Mixed formats are supported.
• Custom Merge Order: Use the up/down arrow buttons to freely arrange your video clips before merging.
• Fast Merge Mode: When all videos share the same format and codec, the tool automatically uses a no-re-encode fast merge for near-instant results.
• Re-encode Mode: For videos with different formats or resolutions, the tool automatically switches to re-encode mode for maximum compatibility.
• Auto Resolution Alignment: If mismatched resolutions are detected, the tool alerts you and lets you choose a reference resolution to scale all clips before merging.
• Flexible Output Settings: Choose output format (MP4/MOV/MKV/WebM/AVI/TS), video codec (H.264/H.265/VP9), quality level, and audio bitrate.
• Real-time Progress: Each file displays its own progress bar and status during processing.
• Preview & Download: Preview the merged video directly in your browser before downloading.

Use Cases

• Combine multiple lecture or screen recordings into a complete course video
• Join several short clips shot on your phone into one cohesive video
• Merge chapter-by-chapter exported videos into a single file for archiving
• Quickly assemble footage clips for social media without professional editing software
• Consolidate multi-part meeting recordings or live stream replays

How to Use

1. Click the upload area or drag and drop your video files onto the page. Multiple files can be added at once.
2. Use the arrow buttons in the file list to arrange the clips in the desired merge order.
3. In the Merge Settings panel, select your preferred output format, codec, and quality (or keep the defaults).
4. If mismatched resolutions are detected, a banner will appear — select your reference resolution and proceed.
5. Click Start Merge and wait for processing to complete, then preview or download your result.

Privacy & Security

This tool is powered by WebAssembly technology. All video processing runs entirely within your browser — no video data is ever sent to a server. It works fully offline, so your files stay private at all times.

Frequently Asked Questions

Why does the merged video have black bars?

When clips have different aspect ratios, the tool scales them to fit the reference resolution while preserving the original proportions, filling any remaining space with black bars to avoid distortion.

How many videos can I merge at once?

There's no hard limit, but due to browser memory constraints, we recommend keeping the total size under 2GB and the number of files under 20 for stable performance.

What's the difference between fast merge and re-encode merge?

Fast merge skips re-encoding entirely, making it nearly instant — but it requires all clips to share the same format and codec. Re-encode merge processes each clip individually for full compatibility, supporting mixed formats and unified output specs, though it takes longer.

What should I do if the merge fails?

Try setting the output format to MP4 with H.264 codec, which resolves most compatibility issues. If it still fails, try reducing the number of files or the resolution of your input videos.

Is there a watermark on the output video?

No. This tool is completely free and adds no watermarks or branding to your output video.