Trim a Video Online
Keep only the useful section of a longer video by setting a precise start and end point before exporting.
Media Tools
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Free Online Tool
Free Online Video Trimmer – Cut MP4 & WebM Video
Trim MP4, WebM and other supported videos online. Choose precise start and end times, output format and quality, then cut the video in your browser.
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Browser-Based
Online Tool
Free Online Video Trimmer – Cut MP4 & WebM Video
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Upload Video
Use a video format supported by your browser and the FFmpeg WebAssembly build.
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The video may still be trimmable. Enter the start and end times manually below.
Export Settings
Selected Duration
Online Video Trimmer
Free Online Video Trimmer
Cut a selected section from a video directly in your browser. Choose precise start and end times, select an output format and quality level, then export the trimmed clip with FFmpeg WebAssembly.
Trim Video
Cut MP4
Cut WebM
Start & End Times
Timeline Preview
Quality Control
Browser Processing
How do I trim a video online?
Upload a supported video, select the start and end of the section you want to keep, choose the output format and quality, then start trimming. CyberTools processes the selected segment with FFmpeg WebAssembly in your browser and prepares the resulting video for download.
Common Online Video Trimming Tasks
Video trimming is useful when you need to remove unwanted beginnings or endings, extract a shorter clip, prepare social-media footage or create a more focused video segment.
Cut MP4 Video
Trim an MP4 source and export the selected segment as MP4 when browser-side FFmpeg can decode the source media.
Cut WebM Video
Choose WebM output when you want the selected clip encoded with a web-oriented video format.
Remove the Beginning of a Video
Move the start point forward to discard an introduction, countdown, recording delay or other unwanted opening footage.
Remove the End of a Video
Move the end point backward to remove unnecessary closing footage without keeping the complete source duration.
Extract a Short Video Clip
Select a smaller section from a longer recording for demonstrations, social posts, previews or focused sharing.
MP4 vs WebM vs MOV for Trimmed Video
The best output depends on playback compatibility, codec support and where the trimmed clip will be used. A container format does not by itself guarantee a specific codec.
| Format | Best For | Current Workflow | Considerations |
|---|---|---|---|
| MP4 | Broad playback and sharing | Video encoded with H.264 and audio encoded with AAC | Encoding requires processing rather than simple byte-level cutting |
| WebM | Modern web-oriented video | Video encoded with VP9 and audio encoded with Opus | Compatibility depends on the target application and device |
| MOV | QuickTime-style container workflows | Output availability depends on the FFmpeg build and source compatibility | Browser and codec compatibility can vary |
| High Quality | Preserving more visual detail | Uses a lower CRF value | Usually produces more encoded data |
| Balanced Quality | General-purpose clips | Uses a moderate CRF value | Balances visual quality and encoded size |
| Smaller Output | Reducing file size | Uses stronger video compression | More compression can reduce visual detail |
How CyberTools Trims Video in Your Browser
CyberTools uses FFmpeg compiled to WebAssembly. The selected source is loaded into FFmpeg’s browser-side virtual filesystem, the requested time range is processed, and a new video file is encoded from that segment.
Start-Time Selection
The selected start time is passed to FFmpeg with the seek option so processing begins at the requested position.
Selected Duration
CyberTools calculates the difference between your end and start times and sends that duration to FFmpeg.
MP4 Encoding
For MP4 output, the current workflow uses H.264 video through libx264 and AAC audio.
WebM Encoding
For WebM output, the current workflow uses VP9 video through libvpx-vp9 and Opus audio.
Quality Control
The selected quality setting changes the CRF value used by the video encoder. Lower CRF generally means higher visual quality and more encoded data.
Browser-Side Result
The completed file is read from FFmpeg’s browser-side filesystem and exposed as a downloadable object URL.
What Settings Should You Use When Trimming Video?
The best settings depend on the destination of the trimmed clip. Consider compatibility, visual quality, output size and processing workload instead of automatically choosing the highest quality.
MP4 with H.264 and AAC is commonly usable across browsers, devices and sharing workflows.
WebM is designed for web media workflows and the current tool uses VP9 with Opus for this output.
Removing unnecessary footage reduces duration and can directly reduce the amount of video that must be encoded.
A lower CRF allows the video encoder to preserve more visual information, though output can become larger.
A higher CRF can reduce encoded data at the cost of some visual detail.
Browser-side FFmpeg must decode and encode media using the memory and CPU available to the current device.
How Duration, Format and Quality Affect a Trimmed Video
Final size is influenced by clip duration, video complexity, source characteristics, selected output codec and encoder quality settings. Trimming alone does not guarantee a particular file size.
Clip Duration
Shorter clips usually contain less media data than longer clips encoded with otherwise similar settings.
CRF Quality
Lower CRF values generally preserve more visual detail. Higher values allow stronger compression and can reduce encoded size.
Video Complexity
Fast motion, noise, texture and frequent scene changes can require more encoded data than simple or mostly static footage.
Output Codec
Different codecs compress video differently, so equivalent-looking MP4 and WebM outputs do not necessarily have the same file size.
Source Quality
Exporting at a high quality setting cannot restore detail that is already missing from the source video.
Source Resolution
The current trimmer does not use trimming as an upscaling process. Cutting a clip does not create additional source detail.
Where Is Your Video Processed?
The current CyberTools Video Trimmer performs its main trimming and encoding workflow with FFmpeg WebAssembly inside the browser.
- The selected video is written into FFmpeg’s virtual filesystem within the browser environment.
- Seeking, decoding, trimming and output encoding use CPU and memory available to your browser and device.
- The completed trimmed file is read from FFmpeg’s browser-side filesystem and made available for download.
- Browser-side processing avoids a conventional remote transcoding workflow for the main trimming operation, but browser memory and codec limitations still apply.
What an Online Video Trimmer Cannot Do
Trimming changes which part of a video is retained. It does not automatically repair damaged footage, improve poor source quality or make every codec compatible with every browser.
- Trimming cannot restore image detail that is missing from the original recording.
- Very large or long videos can require substantial browser memory and processing time.
- Some containers or codecs may not be decodable by the FFmpeg WebAssembly build used by the tool.
- The current MP4 and WebM workflows re-encode video rather than performing a guaranteed lossless stream copy.
- Changing the quality setting cannot create genuine detail beyond what exists in the source.
- For very large media, batch processing or production editing, a desktop video editor or native FFmpeg workflow may be more appropriate.
Video Trimming, Codecs, Containers and CRF Explained
These terms explain why trimming a video involves more than choosing two timestamps and why output compatibility, quality and size can vary.
Video Trimming
Keeping a selected time range from a longer video while removing footage before or after that range.
Container
A file structure such as MP4, WebM or MOV that can contain encoded video, audio and related metadata.
Codec
A method used to encode and decode video or audio data inside a media container.
H.264
A widely used video compression standard used through libx264 for MP4 output in the current workflow.
AAC
The audio codec used for MP4 output by the current CyberTools trimming command.
VP9
The video codec used through libvpx-vp9 for WebM output in the current workflow.
Opus
The audio codec used for WebM output in the current trimming workflow.
CRF
Constant Rate Factor, an encoder quality control where lower values generally preserve more visual detail.
FFmpeg
The media-processing framework CyberTools uses to decode the source and encode the trimmed output.
WebAssembly
A browser technology that allows compiled software such as FFmpeg to execute inside a web page environment.
Video Trimmer FAQ
Detailed answers about trimming MP4 and WebM video, start and end times, quality, codecs, browser processing and output files.
How do I trim a video online?
Upload a supported video to CyberTools, select the start and end times of the section you want to keep, choose an output format and quality, then start trimming. FFmpeg WebAssembly processes the selected range in the browser and creates a new video file for download.
Can I trim an MP4 video?
Yes, when the codecs contained inside the MP4 can be decoded by the FFmpeg WebAssembly build used by the browser tool. MP4 is a container, so different MP4 files can contain different video and audio codecs.
Does trimming reduce video quality?
The current MP4 and WebM workflows encode a new output video, so quality depends partly on the selected CRF setting and codec. A higher-quality setting can reduce additional compression loss, but no export setting can improve detail that is missing from the source.
What do the start and end times mean?
The start time marks where the retained clip begins and the end time marks where it finishes. CyberTools calculates the difference between those values and processes only that selected duration.
Which output format should I choose?
MP4 is useful for broad playback workflows and the current tool encodes it with H.264 video and AAC audio. WebM uses VP9 video and Opus audio and is useful for web-oriented workflows. Choose according to the compatibility requirements of the application or device that will play the result.
What does the quality setting change?
The quality control changes the CRF value supplied to the video encoder. Lower CRF values generally preserve more visual detail and can produce more encoded data, while higher values allow stronger compression.
Does the trimmed video keep audio?
The current MP4 workflow encodes audio as AAC and the WebM workflow encodes audio as Opus when compatible source audio is available. The result therefore differs from animated-image tools such as GIF, WebP or APNG, which do not carry a normal video audio track.
Is my video uploaded to a trimming server?
The current CyberTools Video Trimmer performs its main trimming and encoding process with FFmpeg WebAssembly in the browser. The source is written to FFmpeg’s browser-side virtual filesystem, processed using local browser resources and read back as the finished downloadable file.
Why can a large video fail in the browser?
Browser-side video processing requires memory for the source file, decoded media and encoder working data. Long videos, large source files, high resolutions and complex footage can exceed the resources available to the browser or device.
Is trimming the same as compressing a video?
No. Trimming removes time from a video by keeping only a selected section. Compression focuses on reducing encoded file size. A shorter trimmed video may be smaller because it contains less footage, but trimming and compression are different operations.
Cut and trim video online with precise start and end controls. Export MP4 or WebM with adjustable quality using browser-based FFmpeg WebAssembly processing.
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