No. Each file is converted inside this tab, and the page's security policy blocks it from sending data anywhere.

It reads the first bytes of the file, where most formats sign themselves, and only then looks at the name. A PNG renamed to .txt is still treated as a PNG.

It handles images, audio, CSV, JSON, Markdown and HTML so far. PDFs, Word and Excel files, video and HEIC photos are not supported yet. Request the conversion you need and it goes on the list.

JPEG and BMP can't store transparency, so those areas are filled with white. Choose PNG, WebP or ICO to keep it.

Your picture at the standard icon sizes that fit inside it, from 16 to 256 pixels, fitted into squares without stretching. Windows and browsers pick the size they need.

WAV is uncompressed 16-bit audio. It opens everywhere and suits editing, but it's about ten times the size of an MP3.