How does the tool find a missing apostrophe without a dictionary?

It uses a published list of 27 spellings that only exist without the mark, such as dont and isnt, plus a condition for the three that are also real words. Anything outside that list is not guessed at.

Why was lets you and me go corrected but the plan lets you save not?

Because lets is a real word. The rule waits for the following word: a pronoun or a verb in a request proves the contraction, while a subject and infinitive afterwards proves the ordinary verb, so only the first sentence is flagged.

For the plural decade, the modern convention is 1990s with no apostrophe, so it is flagged as a style point rather than an error. The possessive form, as in the 1990's biggest hits, is accepted as written.

Why does it not check its and it's?

Those are homophones, not apostrophe patterns: both spellings are real, and only the surrounding words say which is meant. The Homophone Confusion Detector owns that pair, and this tool stays quiet on it rather than duplicating a worse rule.

What is the mixed apostrophe styles finding?

It fires when a document contains both the straight mark and the curly one. Both are correct alone, but a draft that switches between them shows in typeset output, so the mix is reported as a typography note.

Apostrophe Error Finder

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The published list

dont → don't · doesnt → doesn't · didnt → didn't · isnt → isn't · arent → aren't · wasnt → wasn't · werent → weren't · hasnt → hasn't · havent → haven't · hadnt → hadn't · couldnt → couldn't · wouldnt → wouldn't · shouldnt → shouldn't · wont → won't · aint → ain't · oclock → o'clock · youre → you're · theyre → they're · theres → there's · thats → that's · whats → what's · heres → here's · wheres → where's · whos → who's · im → I'm · ive → I've · lets → let's

These are the 27 spellings that only exist with an apostrophe. The engine holds nothing else: no general word list, no guessing. If a spelling is not in this list and is not one of the stray-mark or decade patterns, it is not reported.

Three entries are also real words — lets, wont and im — so they fire only when the next word proves the contraction: "lets you and me go" is reported, "the plan lets you save" is not. its and it's, who's and whose, and they're, their and there belong to the Homophone Confusion Detector, which can read the context; this tool deliberately stays out of them.

A missing possessive apostrophe is out of scope. "the students books" needs to know that students is the owner and books the thing owned, and a plural possessive ("the dogs' toys") is accepted as written rather than rewritten.

The Apostrophe Error Finder works from a published list of 27 spellings that only exist without an apostrophe — dont, isnt, couldnt — plus checks for stray marks, doubled marks, decade apostrophes and mixed straight and curly styles.

What is Apostrophe Error Finder?

The most common of all apostrophe mistakes is not a misplaced mark but a missing one: a missing apostrophe leaves a plausible string of letters, so the eye reads straight past it. This apostrophe error finder handles it with a closed list of 27 spellings that are only correct with the mark: dont, doesnt, didnt, isnt, arent, wasnt, werent, hasnt, havent, hadnt, couldnt, wouldnt, shouldnt, theyre, youre, whos and the rest. The list is printed in full on the tool page, so the claim is one you can check line by line.

Three entries are real words on their own — lets, wont and im — and they are marked as needing evidence. A rule for them fires only when the next word proves the contraction: lets you and me go is reported and corrected to let's, while the plan lets you save is left alone. im followed by a verb or an adjective is treated as the contraction; the same logic applies to ive and the other ambiguous forms.

Around that core sit four smaller checks. A decade written with an apostrophe (1990's) is flagged as style, because the modern convention is 1990s, while the possessive form the 1990's fashion is accepted. A stray apostrophe, one sitting where no contraction or possessive can be, is reported as an error; so is a doubled mark such as don''t. The last check reads the whole document for apostrophe styles: if it uses both the straight ' and the curly ’, the mix is reported as a typography issue, since switching between them is visible in print and invisible in the editor.

The engine deliberately stays out of the hardest cases. its and it's, whose and who's, and they're, their and there are context problems rather than apostrophe problems, so they belong to the Homophone Confusion Detector, which reads the surrounding words; a missing possessive apostrophe in the students books needs to know who owns what, which no character pattern can supply; and a plural possessive such as the dogs' toys is accepted exactly as written, never rewritten as dog's.

What remains is a checker with a small, honest scope. It knows 27 spellings, three of them conditionally, and it never guesses at a word it has not been given. That is why it can be trusted on the findings it does produce, and why a clean result means the listed faults are absent rather than that every apostrophe in the draft is correct. A closed list cannot invent an apostrophe mistake, so every finding names a form that is printed on the page and can be checked by hand.

Run it after the wording is settled, and run it on the whole document rather than paragraph by paragraph, so the mixed-style check has enough to compare. Copy report and Download produce a plain list of findings with the suggested fix, which is usually the fastest way to work through a draft that has lost its marks to copy and paste. In a repeated phrase one fix removes many findings, so start with whatever appears most often.

How to use Apostrophe Error Finder

Paste the draft; the published list and the other five checks run as you type.
Fix the missing-apostrophe findings first, starting with the forms that repeat.
Check the lets, wont and im findings in context — the rule needs the next word as evidence.
Read the decade findings and decide whether the style choice is yours to make.
If mixed apostrophe styles are reported, convert the draft to one mark before publishing.

When to use Apostrophe Error Finder vs related tools

Use this finder when the marks in a draft have been through copy and paste and need checking, and use its siblings for the faults it hands over. Contractions that need context — its and it's, whose and who's, their and there — are the Homophone Confusion Detector's job, and mark placement around brackets and quotes is the Punctuation Checker's.

When the apostrophe is right and the capitalisation around it is not, the Capitalization Checker covers sentence starts, the pronoun I and documented names.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.