5 Differences

1. Man, Skyscraper, shadow, differences, road; 2. Flip-flops, road, passerby, skyscraper, paint; 3. Glasses, Claw, Sun, Plaque, Trees; 4. Driver, Dreams, Fats, Productive, Rivet; 5. Path, Grass, Stone, Stone, Reed; 6. Tree, tree, tree, Christmas tree, Christmas tree; 7. Cloud, shadow, rivet, skyscraper, heart; 8. Cloud, branch, branch, shadow, path; 9. Skyscrapers, soles, doors, mannequin, threshold; 10. Arch, door handle, tights, drain, window; 11. Prop, square, or, bird, birds; 12. Brick, brick, brick, shadow, path; 13. Brick, brick, TV, corner, shoe; 14. Ceiling, brick, brick, guitar, cornice; 15. Star, star, tree, soon, marking

Decent game. Find the difference games aren't usually my favorite, but this one at least has nice visuals.

Found a site where it still works: https://www.crazygames.com.br/jogos/5-differences

This SWF file ought to do the trick:
supernova://play/?swfurl=https://chat.kongregate.com/gamez/0000/3459/live/difference.swf?kongregate_game_version=1205904559 (Make sure to copy and paste the entire link, including the "supernova" part right before it!)

Cross-eye technique is the one I used, and my vision isn't exactly perfect (20/40 in one eye and 20/80 in the other if I remember right.) Just treat the screen like those books where you have to cross your eyes to see a 3D image and it makes finding the differences easier.