Do I need LibreOffice installed?

No. Both formats are implemented directly here: ODT is a zip of XML parts and so is DOCX, and the converter reads one into a document model and writes the other out of it. Nothing is shelled out to an office suite and nothing is uploaded.

What does not survive the conversion?

The constructs the two formats genuinely do not share, and each one is listed after the conversion rather than dropped quietly. The usual entries are ODF-specific field types, some frame anchoring, and embedded objects from an office suite that are not images.

Does it work the other way?

Yes — DOCX to ODT uses the same engine in reverse, and the converter also covers RTF, Markdown, HTML, EPUB, plain text and PDF output. The editor itself opens and saves all of them, so a conversion can also be “open it and save as”.

Can I convert a folder of files at once?

Yes. Add several files to the converter and they are processed one after another in the browser, arriving as a single zip. The limit is your device's memory rather than a file count or a tier.

Convert ODT to DOCX Without LibreOffice

An OpenDocument file and a recipient who wants Word format. Convert it in a browser tab, keep the styles and tables, and know what the two formats disagree about.