A lot of good options with varying levels of data they give. The usual go-to is Google Search Console, if it's your own website. There's others like Moz Link Explorer, Ahrefs, SEMrush. Of course to get the most out of a good tool, you usually have to pay the fee so see if that's worth doing. Not sure if they offer trials. They all have different crawlers and databases, so even paid tools often show slightly different backlink profiles. If you're just after a rough idea of a site's authority and backlink profile, the free versions are usually good enough. For serious competitor research or link building, you'll probably have to open your wallet so keep that in mind.