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Spot the Error
Every sentence below has exactly one mistake: a confused word, a grammar slip, a mangled idiom or a misspelling. Find it before the timer runs out, keep your streak alive, and learn the rule behind each one.
Ten sentences. One mistake in each. Ten seconds per sentence. Tap the wrong word and the red pen fixes it.
This game needs JavaScript. Every sentence and its answer is listed below, so you can still play along on paper.
How to play#
- One mistake per sentence. Everything else in the sentence is correct, so trust your first instinct.
- Ten seconds each. The bar drains from green to red. Faster correct answers score more.
- Streaks multiply. Every correct answer in a row adds to your streak bonus. A miss or a timeout resets it.
- Keyboard friendly. Press Tab to move between words and Enter to choose. Press Enter again for the next sentence.
- Share your card. At the end you get a spoiler-free grid of hits and misses to paste anywhere.
What the rounds test#
The sentences are drawn from four of our language guides, so every answer links back to a sourced explanation:
- Commonly confused words: then/than, its/it’s, affect/effect, lose/loose and dozens more. These are real words in the wrong place, which is why a spell-checker waves them through.
- Common grammar mistakes: should of, subject–verb agreement across a long subject, and apostrophes in plurals.
- Misused idioms: tow the line, free reign, sneak peak. Many are eggcorns, mishearings that make a kind of sense.
- Commonly misspelled words: definately, seperate, recieve.
All 36 sentences, with answers
Every round is drawn from this list. Each answer links to the guide that explains the rule.
- My sister is a much better swimmer then anyone else on her team.
Show the error
then→ than. Comparing? Use than. Then is about time or sequence (first this, then that). Confused words guide - The new parking rules will effect everyone who works the night shift.
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effect→ affect. Affect is the everyday verb meaning 'to influence'; effect is usually the noun for the result. Confused words guide - The neighbors said their going to repaint the fence this weekend.
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their→ they're. If 'they are' fits, write they're; their shows possession. Confused words guide - Every morning the cat waits patiently by it's bowl and meows loudly.
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it's→ its. It's always means 'it is' or 'it has'; the possessive its takes no apostrophe, like his and hers. Confused words guide - Hold the railing tightly so you don't loose your balance on the stairs.
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loose→ lose. Lose (one o) means to misplace or fail to win; loose (two o's) means not tight. Confused words guide - Fresh mint is a lovely compliment to a bowl of summer berries.
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compliment→ complement. A complement completes or perfects something; a compliment is praise. Confused words guide - The principle reason for the delay was a shortage of spare parts.
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principle→ principal. Principal is the adjective meaning 'chief'; principle is only ever a noun for a rule or belief. Confused words guide - There were less people at the beach than we expected today.
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less→ fewer. Fewer is for things you can count, like people; less is for amounts you measure. Confused words guide - Let me know if your coming to the picnic on Saturday.
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your→ you're. Expand it to 'you are': if that fits, write you're; your means belonging to you. Confused words guide - Nobody could figure out who's umbrella was left in the meeting room.
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who's→ whose. Who's means 'who is' or 'who has'; whose means belonging to whom. Confused words guide - Our puppy gets far to excited whenever the doorbell rings.
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to→ too. Too means 'also' or 'excessively'; 'too' has too many o's. Confused words guide - Everyone was invited to the party accept my cousin, who was traveling.
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accept→ except. Except means excluding (except excludes); accept means to receive or agree to. Confused words guide - My grandmother gave me some great advise about planting tomatoes.
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advise→ advice. Advice is the noun, a recommendation (it rhymes with ice, a thing); advise is the verb. Confused words guide - We could not decide weather to hike the ridge or stay by the lake.
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weather→ whether. Whether means 'if' and introduces alternatives; weather is atmospheric conditions. Confused words guide - The trains sat stationery for an hour because of snow on the tracks.
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stationery→ stationary. Stationary means not moving; stationery is writing paper (e for envelope). Confused words guide - The chef spent all afternoon baking a chocolate desert for the party.
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desert→ dessert. Dessert is the sweet course (you want seconds, ss); a desert is arid land. Confused words guide - You should of seen the fireworks over the harbor last night.
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of→ have. Should have shrinks to should've in speech and sounds like 'of', but 'should of' in writing is always an error. Grammar guide - I would of called you back, but my phone battery died.
Show the error
of→ have. Would of, could of and should of are always errors; write would have or would've. Grammar guide - The box of old holiday ornaments are sitting in the garage.
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are→ is. The verb must agree with its real subject, box, not the nearest noun, ornaments. Grammar guide - The corner bakery sells fresh muffin's every morning before seven.
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muffin's→ muffins. Don't use an apostrophe to make a noun plural. Grammar guide - The coach handed out new jerseys to Maya and I after practice.
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I→ me. After a preposition like to, use the object form me. Drop the other person: you would never say 'to I'. Grammar guide - The doctor whom we believe is the best in town is retiring.
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whom→ who. Strip out 'we believe': the pronoun is the subject of 'is', so it stays who. Grammar guide - After the long hike, all I want is to lay on the couch.
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lay→ lie. Lay takes an object (you lay something down); lie does not (you lie down). Grammar guide - New employees are expected to tow the line during their first month.
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tow→ toe. To toe the line is to conform, as runners put their toes against a starting mark. Idioms guide - The manager wanted to nip the office gossip in the butt quickly.
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butt→ bud. To nip it in the bud is to stop something early, the way a gardener pinches off a bud before it flowers. Idioms guide - The director gave the actors free reign to improvise the final scene.
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reign→ rein. It's free rein: loose reins let a horse move freely. Idioms guide - The whole crowd waited with baited breath for the final penalty kick.
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baited→ bated. It's bated breath: bate means to lessen or hold back. Idioms guide - The studio released a sneak peak of its new animated film today.
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peak→ peek. It's a sneak peek, because a peek is a look; a peak is a summit. Idioms guide - Irregardless of the forecast, we are still going camping this weekend.
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Irregardless→ Regardless. Irregardless is a nonstandard blend that has never been accepted in Standard English; write regardless. Idioms guide - After years of cheating at board games, he finally got his just desserts.
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desserts→ deserts. It's just deserts: what you deserve, not a sweet course. Idioms guide - I will definately bring snacks for the road trip on Friday.
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definately→ definitely. Definitely contains 'finite'. Spelling guide - Please keep the raw chicken on a seperate cutting board.
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seperate→ separate. There's 'a rat' in separate. Spelling guide - You should recieve a confirmation email within the next few minutes.
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recieve→ receive. Receive is one case where 'e before i after c' holds. Spelling guide - The lakeside cabin is big enough to accomodate our whole family.
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accomodate→ accommodate. Accommodate is big enough to accommodate two c's and two m's. Spelling guide - It felt a little wierd to see snow falling in late April.
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wierd→ weird. Weird is weird: it breaks the i-before-e rule. Spelling guide - Short power outages are a common occurence during summer thunderstorms.
Show the error
occurence→ occurrence. Occurrence has a double c, a double r, and ends in -ence. Spelling guide
Frequently asked questions
How does Spot the Error work?
Each round shows ten sentences, one at a time. Every sentence contains exactly one wrong word. Tap or click it (or move with Tab and press Enter) within ten seconds. A correct tap earns points plus a bonus for speed and streak; the red pen then shows the correction and links to the guide that explains it.
Is it 'affect' or 'effect'?
Usually, affect is the verb meaning to influence and effect is the noun meaning a result. If you can put "the" in front of it, you want effect. The commonly confused words guide covers the exceptions.
Is 'should of' ever correct?
No. It comes from how should've sounds in speech. Write should have or should've. The same goes for could of and would of; see common grammar mistakes.
Why can't a spell-checker catch these?
Many of these mistakes are correctly spelled words in the wrong place, like then for than or reign for rein, so a spell-checker sees nothing wrong. Outright misspellings are usually caught, but spell-checkers aren't everywhere: not on handwritten forms, whiteboards or every text box.
Does the game save my score?
Only your best score, in your own browser's local storage. Nothing is sent to a server, and there is no sign-up.
Sources
Every factual claim on this page links to one of these. Checked October 2026. See how we source.
- Cambridge Dictionary, English Grammar Today: Affect or effect? dictionary.cambridge.org
- Cambridge Dictionary: There, their or they're? dictionary.cambridge.org
- Cambridge Dictionary: It's or its? dictionary.cambridge.org
- Harvard Law School Writing Center: Common language errors hls.harvard.edu
- Purdue OWL: Apostrophe introduction owl.purdue.edu
- The Phrase Finder: For all intents and purposes phrases.org.uk
- Wikipedia: Eggcorn en.wikipedia.org
- Wikipedia: Commonly misspelled English words en.wikipedia.org