This is the official development build of uBlock Origin.
uBlock Origin is NOT an "ad blocker": it is a wide-spectrum blocker — which happens to be able to function as a mere "ad blocker". The default behavior of uBlock Origin when newly installed is to block ads, trackers and malware sites — through EasyList, EasyPrivacy, Peter Lowe’s ad/tracking/malware servers, various lists of malware sites, and uBlock Origin's own filter lists.
The stable version of uBlock Origin is at:
Use this development build of uBlock Origin if you want to help test new fixes since last stable release version, and to help find regression bugs.
Report regression bugs at uBlock Origin issue tracker:
"uBlock Origin Dev Build" does not share any settings with the stable release of "uBlock Origin", they are installed as two distinct extensions. If needed, use the backup/restore feature of uBlock Origin to transfer settings between the two extensions.