Need Feedback on My File Conversion WebApp

UI looks decent, however the UX to convert files looks a bit crowded. I suggest moving the "Supported conversions" section elsewhere.

Like Harvansh said, this might be a bit tricky to monetize. Not only are there several (free) alternatives, your product doesn't necessarily have any advantage over other sites. Try and find something that can make your product stand out. Maybe add integrations with external services, an API, file automations, or something that users may have trouble with that can't be solved with existing products.

SEO is also pretty important for tools like these. Try adding your site to the Google Search Console (https://search.google.com/search-console/about) to track your site's ranking + search performance.

It's pretty cool. Another thing you can do is creating a native mac os or windows app that hooks into the context menu. That I would gladly pay for. So for instance, you right-click a .heic file and you can instantly convert it to png

Monetizing a file converter is tough since there are so many free options out there. Instead of charging for basic features, you could use google adsense or affiliate links for related tools (like PDF editors or cloud storage). Later offering batch processing or automation as a premium feature might work, but most value will probably come from building traffic and collecting emails — you can later monetize that list through targeted offers or partnerships. Keeping it fast and ad-light will help retain users too.

Also, I noticed your site is pretty light on content. If you're aiming to drive organic traffic through search rankings, you’ll need to build out strong, relevant content on your pages and start adding related blog posts.
If you’ve got other traffic strategies in mind, though — respect!