A published book online or in paper form is going to be considered published and will likely make it harder to get the interest of an agent or publisher, at least for that project.
My suggestion is to look into services like betareader.io and betabooks.co.
They have some technical mojo to make it harder for anyone to access your books (you need to invite readers). Since they are fairly known, no publisher will think you've published online.
Also, at least betareader.io has a beta reader program where you might get in contact with willing readers. (You can use your own readers too).
Both have limits to what you can do for free though (number of books and readers).
You could of course create your own beta reader site, but even if you don't tell Google about it or use search index prevention measures (e.g. robots.txt) you still risk one of your readers "spreading the word" or a search engine getting in there and indexing it anyway, and it will likely be considered published by a publisher.
And if you plan to self-publish... well I heard about some guy writing a book and he wanted it to be perfect so he planned to invite 5000 people to read it and use their feedback to make it so.
It made me laugh. If you can get 5000 people to read a blog post you've published or even harder, make them pay for a book, you've pretty much found your pool of potential readers right there.
So, if you plan to self-publish, all worries about if the book should be considered published or not is of course up to you... the worry then is that all your potential customers might read it as betas and then be happy and move on...