Is this bookmarking site useful?

it took me a minute to understand what was different about your service - Perhaps make the explanation simpler and easier to digest?

Here are my first impressions - I hope this is helpful.

I'd consider having a simpler UI here on the home page - I expected just one field where I can enter my first link. I'm not sure it is useful to the potential user to see a detailed explanation, you need to persuade them that they need to try it first. I'm not sure I'd pay for this without a business reason to do so though I'm afraid - there are too many similar competitors, including the bookmark functionality built into browsers, so it needs to be really clear what you offer on top (several points of differentiation would be good).

This phrase should be much bigger perhaps, as I totally missed it scanning down the page and started looking at the images and trying to click on the fields in the images:

Cloud bookmarking for any device and without plugins.

Another thing you could showcase on home would be boards that other people have made, and why they are different from browser bookmarks. A browser plugin might be a nice way to get customers to start using the service.

As I tapped on your link my initial thought was that it would have to be a browser plugin so it’s just as easy as the built in bookmarks. I was surprised that it was plugin free and I really like the way you did it. I don’t think I am your target audience but I just wanted to tell you I really like the ingenuity of the execution. Keep up the good work!

Same as @TaimoorAhmad

Although the landing page is easy to understand I was just skipping text just to find something / somewhere to put a test link and/or copy some url.

I actually tried to copy what I thought was text, to find out it was an image.

Check for instance https://www.gitpod.io/ they use an image just showing how to do it.

For the product itself, while it might be useful, and the price very accessible, I personally wouldn't use it as I use Chrome only and have all my bookmarks there, but that's just me.