Angry Golem (web)     D&D 5e original/official source
Pathfinder 1e Bestiary 1     Pathfinder original/official source
Pathfinder 2e Bestiary 1     Pathfinder original/official source
Critter Cache: Animals And Beasts     D&D 4e original/official source
Critters, Creatures, & Denizens     Dungeon Crawl Classics (no source link)
Animal Archive     d20 (no source link)