工作原理

简单来说

Many online converters do rely on server-side processing: upload a file, convert it in a data center, then return a result. That can be convenient on mobile devices, but it does mean your file leaves your browser.

This site routes supported conversions through your browser instead. WebAssembly runs compiled C and Rust inside your own tab, which keeps the active conversion local for many formats. A local workflow removes upload transport for those paths, but is limited by your device's capabilities.

真正完成工作的是什么

• ffmpeg, compiled to WebAssembly, handles most video and audio flows used on this site, including common container and codec conversions, trimming, and resizing steps.
• MozJPEG, libwebp, libjxl and libaom cover many lossy image encodes. For AVIF, libaom handles AV1 encode quality behavior inside the format; the build is tuned for browser use. PNG re-encoding uses a Rust path in this project instead of a browser canvas path.
• pdf.js reads and renders PDFs; pdf-lib writes them. Merging, splitting and rotating reuse page objects where possible.
• libarchive unpacks common archive formats and is used to repack output when possible.
• libheif decodes HEIC, fonteditor-core edits font containers, and SheetJS handles spreadsheet parsing.

真实存在的局限

在浏览器中运行是有实际代价的，只谈好处而不谈局限并不诚实。

• Large video is capped. Browser workflows are bounded by available memory and decoder constraints. In practice, memory-heavy files can fail before any upload limits become relevant.
• Performance varies. A data-center server often has more cores and thermal budget than a phone or low-power laptop, so some conversions are slower here. Short clips are often quick; long files can still take longer.
• Some conversions genuinely need a server. Some office and e-book flows, advanced OCR pipelines, or formats that need external preprocessors remain marked as non-browser in this deployment and are only shown from server-capable paths.
• The first conversion downloads an engine. Small codecs are typically a few MB; video and audio uses ffmpeg and can take around 12–30 MB, then stays cached for the next job.

验证隐私声明

You can verify this in browser tools: open the network panel and convert a file. You should see the converter loading a small set of engine assets; for browser-based conversions there is no file upload payload. If needed, run once with a very small sample and confirm the behavior on your own network.

跨源隔离

Multi-threaded ffmpeg can use SharedArrayBuffer, and browsers expose that under cross-origin isolation headers. Isolation can affect third-party content loading behavior, so performance settings are tuned for the current deployment configuration.

When ads are enabled, this deployment keeps isolation off for broader page compatibility. ffmpeg then uses the single-threaded WebAssembly path; it is still functionally equivalent and may be slower on large jobs.