Is grabify safe?

You asked - Is grabify safe? So, Don't worry, your phone is not hacked.

Essentially they send you a tracking link and they know from which IP address this link was accessed. They then can match this IP address to your ISP, and might infer a more or less precise location depending on how your ISP assigns IP addresses. This is the kind of information which is visible by any website you visit, i.e. these are not actually secret private information. While the attacker could for example try to DDoS you it is likely more to just scare you in this case. Don't be scared.

You can see for yourself what the "attacker" and also any website you visit can see. Just create your own link at grabify, visit it and check the result. I've tried myself and for example the location is way off (another town) and the claimed device name is actually only its IP address again. Not actually impressive and nothing to worry about. Depending on the capabilities of your device this might also include the battery level etc. Again, this information is not really secret but might be used to scare you since you don't expect the "attacker" to know this and wonder what else they know. Best check yourself.