If you're not technical: use the free online tool
If you're not a technical person and you're looking for a free way to make a video smaller, use my online video compressor. Choose your video, enter a target size or adjust the quality, then convert and download it. No installation or account is needed.
For a strict upload limit, aim slightly below the maximum and check the downloaded file. Reducing the resolution can help, but keep text and important details readable.
If you're technical and prefer a command-line workflow, I'll show an FFmpeg example after the browser steps.
How to reduce a video's file size
- Open Video compressor and choose your video.
- Enter a target size in MB if you have a specific upload limit, or use the quality controls.
- Choose MP4 as the output if that suits the receiving service.
- Open More settings and enable Resize during compression if a smaller resolution is appropriate.
- Select Convert and wait for processing to finish.
- Check the downloaded video's size, picture and audio before sharing it.
For a service with a strict limit, aim a little below it. A target is an encoding goal, and container overhead and processing choices can affect the final size.
If you're technical: how it works
If you're technical, you can re-encode a video locally with FFmpeg. For an ordinary video with optional audio, and an FFmpeg build containing libx264 and AAC support:
ffmpeg -i input.mp4 -map 0:v:0 -map '0:a:0?' -c:v libx264 -crf 26 -preset medium -c:a aac -b:a 128k -movflags +faststart output.mp4 This selects the first video stream and, if present, the first audio stream. It encodes H.264 video and AAC audio into MP4. It does not preserve additional streams such as subtitles.
CRF controls the quality tradeoff; it does not request a fixed number of megabytes. With this encoder, increasing CRF generally reduces size and quality. Compare the output with the original rather than assuming every source will get smaller.
For a size target, estimate the combined bitrate budget from duration, reserve some for audio and overhead, and use an appropriate bitrate-controlled workflow. My browser tool provides size-target controls so users do not need to calculate that manually.
Why duration matters as much as resolution
As a rough planning rule:
file size ≈ duration × combined video-and-audio bitrate ÷ 8 For example, a 60-second video with a total bitrate of 2 megabits per second needs roughly 15 megabytes before container overhead.
This explains why a long recording needs a much lower bitrate than a short clip to fit the same size limit. A target that looks reasonable for 30 seconds may look poor when spread across ten minutes.
If only part of the recording is needed, trimming unnecessary time can help more than aggressive compression.
Should you lower quality or resolution?
Start with the content.
A talking-head clip viewed on a phone may still look useful at 720p. A screen recording with tiny code or spreadsheet cells may need more resolution to keep the text readable.
Lowering quality too far can create blocks, smearing and lost detail. Lowering resolution removes pixels, which can make small text unreadable even if the image looks smooth.
Test a representative result. Check the most demanding moment: a busy scene, scrolling text or a frame with fine detail.
MP4 alone does not mean a small file
MP4 is a container, not a file-size setting.
Two MP4 files with the same duration can differ greatly in size because their encoded bitrates, resolutions, frame rates and audio settings differ.
Choose the output format for compatibility, then use the compression controls to manage size. Simply converting an existing video to MP4 does not guarantee a reduction.
Browser processing has practical limits
The video is processed on your device rather than submitted to a conversion server. The site uses browser media processing, including a WebAssembly-based FFmpeg path where needed.
Large or lengthy videos can still take time and require substantial memory. Keep the tab open, and remember that local processing depends on your device's capabilities.
Keep the original. Once you remove detail through lossy compression, the smaller file cannot bring it back.
What do you compress most often: phone videos, screen recordings or clips for a website?
