Can you recommend a safe and free ad blocker program?

Which browser?

I use AdGuard on Google Chrome. It serves my needs.

Adblock (on Chrome)

along with Privacy Badger to stop trackers

Adblock on Chrome also and Ghostery to stop tracking.

You didn’t specify for what application or device.

I use Firefox Adblock Plus.

Firefox Adblock Plus here too. Seems to work very well, and it’s easy to set exceptions immediately from the main screen, etc.

Thanks so much y’all.

uBlock Origin is the king of blocking right now. It is available for Firefox and Chrome.

I also use Ghostery but just be warned that Ghostery will break some sites.

You people are the most awesome in the world! Thank you very much.