✂️ 视频裁剪（画面裁切）Video Cropper

使用说明与常见问题How-to & FAQ

「视频裁剪（画面裁切）」是什么？What is the Video Cropper tool?

裁掉视频画面的黑边、水印区域或多余部分：在预览上拖动和缩放裁剪框，或直接输入像素坐标，一键套用 1:1、9:16（抖音/Reels）、16:9、4:5 等比例，同时可截取开始和结束时间，保留声音，本地导出。Crop black bars, a corner or unwanted areas out of a video frame — drag and resize the crop box on the preview or type pixel values, snap to 1:1, 9:16 (TikTok/Reels), 16:9, 4:5 and more, trim start and end, keep the audio, and export locally.

如何使用「视频裁剪（画面裁切）」？How do I use the Video Cropper tool?

在「视频裁剪（画面裁切）」中，按需设置「比例」、「X」、「Y」、「宽」、「高」等选项，然后点击「裁剪并导出」、「停止」按钮即可。支持拖放文件。In the Video Cropper: Set "Aspect ratio", "X", "Y", "Width", "Height", then click "Crop & export", "Stop". Drag-and-drop files is supported.

怎样精确设置裁剪区域？How do I set the crop area precisely?

拖动预览上的蓝框移动位置，拖动右下角圆点改变大小；也可以在 X、Y、宽、高中直接输入原视频的像素坐标。选择比例后，裁剪框会按该比例居中并保持比例缩放。裁剪框的宽和高会自动取偶数（视频编码要求，向下取整，不会超出画面），输出尺寸与裁剪框一致；宽度超过 1920 像素时按比例缩小到 1920。Drag the blue box on the preview to move it and the round handle at the bottom-right to resize; or type X, Y, width and height in source-video pixels. Picking an aspect ratio centres the box at that ratio and keeps it while resizing. The box width and height are rounded down to even numbers (an encoder requirement, never beyond the frame), so the output matches the box; wider than 1920 px is scaled down to 1920.

横屏视频怎么改成竖屏（9:16）？How do I turn a landscape video into 9:16 portrait?

选择比例“9:16”，裁剪框会在画面中央生成最大的竖屏区域，把它拖到主体所在位置后导出即可，适合抖音、快手、Reels 和 Shorts。Choose the 9:16 ratio; the largest portrait area appears in the centre — drag it over the subject and export. Ideal for TikTok, Reels and Shorts.

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.

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.

「视频裁剪（画面裁切）」免费吗？需要注册吗？Is the Video Cropper free? Do I need an account?

「视频裁剪（画面裁切）」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 Cropper is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.