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Progressive Comparison
The direct answer: a must-hit-by progressive publishes a ceiling and is forced to pay before the counter passes it, so its value is readable and can be an advantage play. A mystery progressive fires at a hidden, random trigger with no published cap, so a climbing counter tells you nothing. Only one is worth scouting.
Both types add a slice of every wager to a counter and both hide the exact spin the jackpot will land on. The single difference that decides whether you can beat it is the ceiling.
Must-Hit-By
The machine picks a trigger value at random between the reset (floor) and a published ceiling. As players feed the counter upward, the band of remaining possible trigger points narrows. By the time the counter is near the ceiling, only a small slice of the range is left, so the jackpot is statistically close and the expected cost to force it is low. That gap between the current counter and the ceiling is the entire advantage-play read.
Mystery / Unbounded
The machine also picks a random trigger, but the maximum is not disclosed and the display shows no ceiling. Because you cannot see where the top of the range is, you cannot know how much of it has already been eliminated. The counter could sit far below its hidden cap for a long time. Watching it climb gives you no edge.
The One-Sentence Rule
If a ceiling is printed on the machine, it is a must-hit-by and you can evaluate it. If no ceiling is printed, treat it as an unreadable mystery and move on.
| Factor | Must-Hit-By | Mystery (Unbounded) |
|---|---|---|
| Ceiling shown | Yes — published on the machine | No — hidden |
| Counter is a tell | Yes — closer to ceiling = closer to paying | No usable tell |
| Value calculable | Yes — from the counter and ceiling | No |
| Advantage-play target | Yes, when elevated | Generally no |
| Best time to play | Counter near the ceiling | There is no readable best time |
Want the deeper version of each side? Read the must-hit-by complete guide and the mystery jackpot guide.
Run the Slots documents the trigger threshold and ceiling behavior for 204+ must-hit-by machines, so you never mistake an unreadable mystery pool for a real play.
View PricingA must-hit-by progressive displays a ceiling value on the machine and is forced to award the jackpot before the counter can pass that ceiling. Because the ceiling is published, you can calculate how close the jackpot is and whether the play is player-favorable. A mystery progressive fires at a randomly selected trigger somewhere below an undisclosed cap. Nothing is published, so a rising counter carries no usable information. In short: the must-hit-by is readable and can be an advantage play; the mystery is not.
Not quite, and the naming causes confusion. Some manufacturers label a must-hit-by jackpot as a mystery jackpot on the screen because the exact trigger point is hidden. The distinction that matters for advantage play is whether a ceiling is published. If the machine shows a Must Hit By, Wins By, or Awards Before amount, it is a bounded must-hit-by and the counter is readable. If it only shows a rising number with no stated maximum, treat it as a true unbounded mystery and assume no tell exists.
No. Because the trigger is randomly chosen below a cap you cannot see, a mystery progressive at a high counter value is not statistically closer to paying in any way you can measure. Watching an unbounded mystery counter climb tells you nothing actionable. The only progressives worth scouting by counter position are must-hit-by progressives with a published ceiling.
Because the jackpot cannot exceed the published ceiling, the range of possible trigger points shrinks as the counter climbs. When the counter sits near the ceiling, the expected cost to force the jackpot is low relative to the jackpot itself. That is a calculable positive expected value situation. On every guide at Run the Slots, the exact trigger threshold for each machine is the number that turns this general principle into a go or no-go decision.
Read the progressive display carefully. Look for an explicit ceiling label: Must Hit By, Must Award By, Wins By, or a paired current-and-maximum layout. If a ceiling is present, it is a must-hit-by and you can evaluate it. If only a single climbing number appears with no stated maximum, it is a mystery pool and there is no usable counter tell.
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