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Free bet slip checker · NBA + NFL
Bet slip checker: check your parlay before you bet
Screenshot your slip, or paste it. Slip Surgery reads every leg, checks it against the current FanDuel and BetMGM lines, flags anything that changed, shows you the real odds and the weakest leg, then loads the fixed slip into FanDuel or BetMGM in one tap.
What the bet slip checker does
Reads any slip
Upload a screenshot from FanDuel, BetMGM or another book, or paste the text. Player props and game lines are pulled out leg by leg.
Checks every leg is live
Each leg is matched to today's FanDuel and BetMGM lines. Moved lines, ruled-out players, started games and markets a book doesn't offer get flagged.
Shows the real odds
The implied probability of every leg and of the whole slip, so you see what the payout is really asking for.
Gives a second opinion
Where we model the stat, FanDuel's price is compared with a projection built from a second source, recent form and defense vs position.
Finds the weakest leg
The leg dragging the slip down is called out, with a suggested swap from today's board.
Loads it in one tap
Tap FanDuel or BetMGM and the checked legs land in that book's bet slip. You still confirm the bet in the app.
How to check a parlay in 3 steps
- Upload a screenshot or paste the text. Open Slip Surgery and drop in a screenshot of your FanDuel, BetMGM or any other book's slip, or paste the legs as text. The image is read in your browser.
- Review the flags. Every leg is matched to today's FanDuel and BetMGM lines. Moved lines, ruled-out players, started games and markets a book doesn't offer are flagged.
- Fix the weak spot, then load it. See each leg's implied probability, our model's read where we have one, and a suggested swap for the weakest leg. Then tap FanDuel or BetMGM to load the slip.
Worked example: a 4-leg NBA slip
This is an illustrative slip with made-up players and prices, to show what the checker looks at. It is not a pick.
| Leg | Price | Implied chance | What the check shows |
|---|---|---|---|
| Guard A, over 27.5 points | −115 | 53.5% | OK line unchanged, model and second source both over |
| Center B, over 11.5 rebounds | −130 | 56.5% | OK line unchanged |
| Wing C, over 2.5 threes | +130 | 43.5% | Weakest leg listed questionable; model below the price |
| Forward D, over 6.5 assists | +120 | 45.5% | OK soft matchup by defense vs position |
As built: 4 legs pay about +1574. That price implies a 6.0% chance (about 1 in 17) of all four landing, and it is built on a leg with an injury question.
After the fix: drop Wing C and the slip pays about +628, which implies 13.7% (about 1 in 7). Smaller payout, but every leg left is one you'd bet on its own, and you can still swap in a different leg the checker suggests.
Checking a slip by hand vs using the checker
| Step | By hand | Slip Surgery |
|---|---|---|
| Confirm players are active | Search each injury report | Flagged automatically from ESPN's injury report |
| Confirm the line hasn't moved | Re-open each market in the app | Matched to current FanDuel and BetMGM lines |
| Implied probability | Convert every price by hand | Shown per leg and for the slip |
| Second opinion | Find a projection, compare to the line | Model vs price where we model the stat |
| Weakest leg and a swap | Guesswork | Called out with a suggested swap |
| Rebuild the slip in the book | Tap every leg again | One tap to FanDuel or BetMGM |
Prefer the math yourself? The parlay odds calculator does the payout, implied probability and no-vig fair odds for any slip.
Fix my parlay: what to do with a weak leg
Most slips that look bad have one problem leg: a player who's now questionable, a line that moved a point, or a long price added for the payout. You have four fixes: drop it, move it to an alternate line, swap to a different player or stat in that game, or bet it on its own. Each one changes the payout differently; the full guide has the numbers.
What the checker won't do
- It won't tell you a slip will win. Nothing can; these are model reads, not locks.
- It only covers the NBA and NFL, and only links to FanDuel and BetMGM.
- Prices are captured at build time from Michigan lines. Lines move, so always confirm in the app before you bet.
Parlay guides
Frequently asked questions
Is there a free bet slip checker?
Yes. Slip Surgery is free with no account and no card. Upload a screenshot or paste your NBA or NFL slip and it checks every leg against current FanDuel and BetMGM lines.
How do I know if my parlay is good?
Check four things: every leg is still live at the line you think (player active, game not started, line not moved), each leg is priced fairly on its own, the legs don't work against each other, and the total price is worth the much lower chance of every leg landing. Our 7-step parlay check walks through it.
Can a parlay checker tell me if my parlay will hit?
No, and you should be wary of any tool that says it can. A checker can show you the price, the implied chance of each leg and of the whole slip, what changed since you built it, and where a model disagrees with the book. The game still decides the result.
How do I fix my parlay if one leg looks bad?
You can drop the leg, move it to an alternate line, swap it for a different player or stat, or bet it on its own. Slip Surgery suggests a swap for the weakest leg. See how to fix a parlay with a bad leg for what each option does to your payout.
Does it work with FanDuel and BetMGM?
Yes. Legs are matched to FanDuel and BetMGM (Michigan) lines, and one tap loads the checked slip into either book's bet slip. You can check a screenshot from any book, but the links only go to FanDuel and BetMGM.
Does it check same game parlays?
Yes. Legs from the same game are loaded as a Same Game Parlay and the book sets the final odds, because same-game legs are correlated. Read same game parlay correlation, explained.
Is my screenshot uploaded or stored?
No. The screenshot is read on your device with an in-browser text reader (Tesseract.js). The image is never sent to our server.
Which sports and bets does it check?
NBA and NFL only: player props (points, rebounds, assists, threes, yards, receptions, touchdowns and combos) and game lines (moneyline, spread, totals).
How many legs should a parlay have?
Fewer legs means a higher chance of the slip landing and less of the book's margin stacked up. See how many legs a parlay should have for the numbers.
Check your slip now
Free, no sign-up. Screenshot in, checked slip out.
Model picks, not locks. No checker can tell you a slip will win; it can only show you the price, the math and what changed. 21+ only. If betting stops being fun, call 1-800-GAMBLER or read our responsible gaming page.