WebM Merger Online

Add WebM clips, reorder, merge, download.

1. 1

   Add WebM

   Select multiple WebM files.

2. 2

   Arrange

   Set the clip order.

3. 3

   Merge

   Join them into one output file.

4. 4

   Download

   Save the merged video.

Join web-friendly clips, then export with the settings you need — locally.

WebM is an open, royalty-free web format (often VP8/VP9 video with Opus/Vorbis audio). Merging WebM is great for web-first assets and efficient streaming.

When to use

Use WebM for web delivery or when you prefer open formats. Use MP4 for iOS/Safari and universal playback. Use MOV for Apple-only pipelines.

Compatibility

WebM plays well in Chrome/Firefox/Edge and on Android. For Safari/iOS viewers, export MP4.

Most online video mergers re-encode everything, because they run on a server and have no other option. That costs a generation of quality on every join, and it is why merged files so often come back larger and softer than the clips that went into them. This tool checks first, and when the clips already agree it copies their existing video data straight into the new file — the picture that comes out is the picture that went in.

When clips are joined without re-encoding

• Every clip uses the same video format and the same frame size.
• Every clip has audio in the same format, or no clip has audio at all.
• You have not chosen a transition, a different resolution or a different frame rate.
• The output container can carry that video format — MKV can carry anything, which is why it is offered.

When a re-encode is needed instead

• The clips are different sizes or shapes, so they have to be drawn into one common frame.
• The clips came from different sources and use different video formats.
• Some clips have sound and others do not, so silence has to be created for the quiet ones.
• You asked for a crossfade, a specific resolution or a specific frame rate.

WebM-to-WebM can preserve quality when no re-encoding is needed. Mixing formats may require re-encoding; choose higher quality presets.

Example use cases

• Join browser-recorded WebM clips.
• Combine VP9 exports for web playback.
• Merge game captures for download.

Best practices

• Use MP4 output for iOS if unsure.
• Keep WebM originals until verified.
• Avoid lossy-to-lossy chains when possible.

Common use cases

• Web: One WebM for playback.
• Capture: Screencasts combined.
• Android: Efficient streaming delivery.
• Share: Convert to MP4 when needed.
• Archive: Bundle parts into one.

Powered by optimised video encoding pipelines.

A file's extension tells you very little about whether it can be opened — an MP4 can hold any of half a dozen different video formats, and which of them your browser can read depends on your device. So the supported list here is a closed one, checked when you pick a file rather than after you have waited for it.

What you can put in

• MP4 — the common case, from phones, cameras and most editors.
• MOV — QuickTime, which is what iPhones and Macs record.
• WebM — usually from screen recorders and online recording tools.
• MKV — a container that can hold almost anything, common for longer recordings.

What is refused, and why

• AVI, WMV, FLV, MPEG, OGV and 3GP are refused when you pick them, with the format named.
• These are older containers whose video formats no browser can decode, so no online tool of this kind can open them on your device — trying another browser will not help.
• The refusal happens immediately and points you at a converter, rather than starting work that cannot finish.

All video formats (MP4, WebM, MOV)

• MP4 Merger Online
• MOV Merger Online

• Video merger
• Video compressor
• Video cutter
• Video to GIF
• GIF maker