工作原理
拖放 MP4，选质量，下载 WebM。FFmpeg 在 Web Worker 本地运行。 该工具需要首次一次性下载本地处理引擎（Web Worker）。根据网速可能需要片刻，但可确保零服务器上传与完全隐私。
用质量滑块将 MP4 转为 WebM。
将文件拖放到此处
Up to 2GB · 5 files / batch
MP4 and M4V files.
拖放 MP4，选质量，下载 WebM。FFmpeg 在 Web Worker 本地运行。 该工具需要首次一次性下载本地处理引擎（Web Worker）。根据网速可能需要片刻，但可确保零服务器上传与完全隐私。
Conversions run in your tab with JavaScript — no desktop app required.
Files stay on your device during processing. We do not receive your uploads.
Heavy codecs and AI models run locally via Web Workers and WASM (FFmpeg.wasm, Transformers.js).
拖放 MP4，选质量，下载 WebM。FFmpeg 在 Web Worker 本地运行。 该工具需要首次一次性下载本地处理引擎（Web Worker）。根据网速可能需要片刻，但可确保零服务器上传与完全隐私。
4K 或超长源可能超出内存。不支持 DRM。 处理 100% 在浏览器内离线完成——文件不会离开您的设备。
Yes. This tool is free convert online with no signup. Processing stays in your browser — no uploads.
You control quality settings. Choose higher quality for no quality loss when converting online.
Every conversion runs inside your browser tab using JavaScript and Web Workers. There is no background server queue and no account is required for core tools.
Your files are never uploaded to FreeConvertKit for processing. Originals, previews, and exports stay on your device unless you choose to download or share them yourself.
When codecs or AI models are needed, WebAssembly modules such as FFmpeg.wasm and Transformers.js execute locally — giving you desktop-class power with absolute file privacy.