SpotDiff
Spot-the-difference puzzles for cognitive fitness
SpotDiff is a browser-based spot-the-difference game built around real cognitive training principles. Two near-identical images appear side by side, and your job is to find the hidden differences — a task that draws on sustained attention, selective attention, and visual working memory.
Play SpotDiff — new puzzles daily, no download required.
How it works
Each puzzle presents two complex scenes with a set number of subtle differences hidden between them. You scan both images, compare them region by region, and tap or click on each difference you find. A timer and difference counter track your progress so you always know how close you are to finishing.
Designed for short sessions
Most people don't sit down intending to do "cognitive training" — they open a puzzle app for two or three minutes between other things. SpotDiff is built around that reality. Each puzzle is scoped to be completable in a short session, with a visible timer and difference counter so you always know exactly how close you are to finishing.
This also matters for the attention-training angle: a short, complete task with a clear finish line encourages the kind of focused engagement that a longer, open-ended activity often doesn't.
Difficulty progression
A flat difficulty curve — every puzzle roughly as easy as the last — gets boring fast and stops offering much of a cognitive challenge once you're familiar with the format. SpotDiff is structured in tiers: early puzzles use larger, higher-contrast differences that are easy to spot, while later puzzles shrink the differences, increase visual clutter, and reduce the contrast between the changed area and its surroundings.
This keeps the challenge appropriately matched to a player's current skill level — a task that's neither too easy nor too hard is the one most likely to actually build the skill it targets.
The cognitive skills involved
- Sustained visual attention — holding focus on a scene for an extended period, without your eyes drifting or concentration lapsing.
- Selective attention — filtering out irrelevant detail and prioritising the regions most likely to contain a change.
- Visual working memory — briefly holding a mental snapshot of a region in one image while checking the corresponding region in the other.
- Change detection — forcing a deliberate, effortful kind of scanning rather than relying on automatic movement detection.
Who SpotDiff is for
- Anyone who enjoys puzzle or brain-training games and wants something quick, visual, and low-pressure.
- People looking for a short mental break that's more engaged than passive scrolling but doesn't require a big time commitment.
- Students and professionals who want a quick attention "reset" between focused work sessions.
- Anyone curious about their visual attention and who enjoys tracking improvement in completion time and accuracy over repeated play.
An honest note
While the skills SpotDiff exercises — sustained attention, selective attention, visual working memory — are real and well-documented cognitive functions, the broader claim that any single brain-training game measurably and durably improves general intelligence is genuinely contested in the scientific literature. Some studies show task-specific improvement (you get better at the game itself, and at very similar tasks); the evidence for that improvement transferring broadly to unrelated areas of thinking is much weaker.
We built SpotDiff because it's a well-grounded, evidence-informed way to exercise specific visual attention skills in an enjoyable format — not because we're claiming it will make you smarter in some general, all-purpose sense.
Ready to play?