Fonts like Preeti, Kantipur and PCS Nepali that pre-date Unicode adoption. Instead of real Devanagari code points, they map Nepali glyphs onto ASCII positions — which is why the "text" ends up looking like g]kfn without the matching font installed.
It's not random — those are the exact ASCII slots the legacy font expects. Paste the output into Word or Google Docs, apply the Preeti (or Kantipur / PCS) font to that text, and it redraws as clean Nepali.
Hit Copy legacy text above, open Word, paste, select everything you just pasted, and change the font to Preeti (or Kantipur / PCS Nepali). If the font doesn't show up in the dropdown, you'll need to install it on your computer first.
Match whatever the receiving document, template or office already uses. Preeti is the everyday default in Nepali offices; Kantipur is common in newspaper and print media; PCS Nepali turns up mainly in older government software. If you're unsure, ask the person on the other end which font their template is set to.
The Department of Information Technology (DoIT) and several Nepali government portals distribute Preeti, Kantipur and PCS Nepali for free. A quick search for Nepal government Nepali fonts download will turn them up. Install the TTF files and they show up in Word's font list right away.
Yes to both. All mapping happens in JavaScript inside your browser, so once the page has loaded you can even disconnect from the internet. Nothing is uploaded or stored — handy for confidential drafts, legal paperwork or anything you wouldn't paste into a random online service.