🗜️ 视频压缩（减小视频文件大小）Video Compressor

使用说明与常见问题How-to & FAQ

「视频压缩（减小视频文件大小）」是什么？What is the Video Compressor tool?

在浏览器里压缩 MP4、MOV、WebM 视频：可按目标文件大小（例如压到 25 MB 以内发邮件或聊天）或按画质档位压缩，降低分辨率到 1080p/720p/480p，调整音频码率或去掉声音，还能只截取一段，处理前预估大小。Compress MP4, MOV or WebM videos in your browser — aim for a target file size (e.g. under 25 MB for email or chat) or a quality level, downscale to 1080p/720p/480p, lower the audio bitrate or drop the sound, and optionally keep just one segment, with a size estimate before you start.

如何使用「视频压缩（减小视频文件大小）」？How do I use the Video Compressor tool?

在「视频压缩（减小视频文件大小）」中，按需设置「方式」、「目标大小 (MB)」、「画质」、「分辨率（短边）」、「音频码率」等选项，然后点击「开始压缩」、「停止」按钮即可。支持拖放文件。In the Video Compressor: Set "Mode", "Target size (MB)", "Quality", "Resolution (short side)", "Audio bitrate", then click "Compress", "Stop". Drag-and-drop files is supported.

能压缩到多小？How small can it get?

选“按目标大小”并填入想要的 MB 数，工具会据此计算码率；同时降低分辨率（如 720p 或 480p）画质会更好。目标太小时会提示最低可行大小。浏览器编码器只能按平均码率控制，第一遍常有偏差（画面简单时偏小）；如果偏差超过 ±15%，工具会按实测码率自动再压一遍（处理时间相应加倍），完成后显示实际偏差。画面非常简单或非常复杂时，即使两遍也可能达不到 ±15%，结果里会如实说明。这里的 MB 按 1 MB = 1024 × 1024 字节计算。Choose Target size and enter the MB you want; the bitrate is calculated from it. Lowering the resolution as well (e.g. 720p or 480p) keeps the picture cleaner. If the target is too small you'll be told the minimum. The browser encoder only controls the average bitrate, so the first pass is often off (smaller for simple footage); if it misses by more than ±15%, a second pass runs automatically with a bitrate corrected from the measured result (doubling the processing time), and the actual deviation is shown. Very simple or very complex footage may still miss ±15% after two passes, and the result says so. 1 MB here is 1024 × 1024 bytes.

为什么处理时间和视频长度差不多？Why does processing take about as long as the video?

浏览器没有开放快速转码接口，本工具通过“边播放边录制”重新编码（MediaRecorder），所以耗时约等于所选片段的时长，处理期间请保持页面在前台。好处是完全本地、无需上传。输出格式优先 MP4（新版 Chrome / Edge / Safari），不支持时为 WebM；WebM 在部分播放器里可能不能拖动进度条。Browsers expose no fast transcoding API, so this tool re-encodes by playing and recording at the same time (MediaRecorder); it takes about as long as the selected clip — keep the tab in the foreground. The upside is it's fully local, with no upload. Output is MP4 where supported (recent Chrome / Edge / Safari), otherwise WebM, which some players can't seek.

压缩后的视频为什么没有变小？Why isn't the result smaller?

如果原视频本来码率就很低（例如已经压缩过的手机录屏），再次编码不一定能更小，工具会提示你保留原文件。降低分辨率、选择“小文件”画质或去掉声音通常能明显减小体积。If the original already has a low bitrate (e.g. a compressed phone recording), re-encoding may not shrink it, and you'll be told to keep the original. Lowering the resolution, picking the Small quality or dropping audio usually helps a lot.

视频会上传到服务器吗？Is my video uploaded?

不会。所有处理都在你的浏览器里完成，文件不会离开你的设备，所以也不受上传大小和网速限制（但受电脑内存和性能限制）。No. Everything runs in your browser and the file never leaves your device, so there are no upload limits or waits — only your computer's memory and speed.

「视频压缩（减小视频文件大小）」免费吗？需要注册吗？Is the Video Compressor free? Do I need an account?

「视频压缩（减小视频文件大小）」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Video Compressor is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.