If you've come across api.eu1.fullview.io and are wondering whether it's safe to use, the short answer is that there's not enough working evidence to go on. This address currently returns a 404 error — it's not serving any content, so there's nothing to test or review. That alone makes it hard to recommend trusting the service with any data or requests.
For an API endpoint, you'd typically expect some documentation, a status page, or at least a way to contact the team. None of that exists here. The domain is hosted on Amazon Web Services and uses a valid SSL certificate, which are positive signs, but the lack of any visible owner or operational website outweighs them.
If you were directed to use this API by a third party, treat it with caution. Without a clear operator or any proof the service actually works, it's impossible to say whether api.eu1.fullview.io is legitimate or a front. Look for alternative services that provide contact details, a track record, and a functioning product.