Use paid one like ahref. Free ones are useless.
Some additional recommendations. You can do your own research on these and come to a decision yourself:Use paid one
go with SEMrush, free trial for 7 daysJust for checking and free you can use: https://ahrefs.com/de/backlink-checker
Also with Semrush free you have like 10 free actions every 24 hour to check backlinks
did you purchase them or you reached out to the site owner for these?I have a feeling that I have been getting some of my guest post posted on spammy sites. Could you suggest a good ideally free back link checker.
Even semrush gives some free searches but one will always run out as lot of data is needed.I think you can use Ahrefs for free if you connect your GSC and it's just for one site. I emphasise the word ' think', as we have paid plans.
Those 10 free actions evaporate before we start doing the correct research.Just for checking and free you can use: https://ahrefs.com/de/backlink-checker
Also with Semrush free you have like 10 free actions every 24 hour to check backlinks