“its” vs. “it's”
If you can expand the word to "it is" or "it has" and the sentence still makes sense, write "it's"; if the sentence is showing possession, write "its" with no apostrophe at all.
its
"Its" is a possessive pronoun, showing that something belongs to or is associated with "it" ("the dog wagged its tail"). Like "his" and "her," it never takes an apostrophe, because none of English's possessive pronouns do (my, your, his, her, its, our, their). Historically, English possessive pronouns never took apostrophes even in Old and Middle English, when apostrophes as a punctuation mark didn't exist yet at all; the modern rule that possessive nouns take an apostrophe ("the dog's bone") is a much later printers' convention from the 1600s-1700s that was never extended to the older, already-established possessive pronoun system.
it's
"It's" is a contraction, standing in for "it is" or "it has" ("it's raining"; "it's been a long day"). The apostrophe here marks omitted letters exactly the way it does in "don't" (do not) or "can't" (cannot) — a contraction rule, not a possession rule. "It's" is a comparatively young contraction, only becoming common in written English during the 17th and 18th centuries as printers began using apostrophes more systematically to mark contracted forms in everyday prose, well after "its" had already been functioning as a possessive without one for centuries.
The real distinction
This is the single most common apostrophe error in English precisely because every other possessive in English does take an apostrophe ("the dog's tail," "Sarah's book"), which makes "its" feel like it's missing something. But possessive pronouns are a separate, closed grammatical category from possessive nouns, and none of them — his, hers, its, ours, yours, theirs — ever takes an apostrophe. The apostrophe in "it's" is doing an entirely different job: marking a contraction, the same job it does in "won't" or "they're." This mix-up is consistently ranked among the top three or four most common punctuation errors by copyediting and grammar-checker research, alongside "your/you're" and "there/their/they're," precisely because it violates writers' strong, generally reliable instinct that possession requires an apostrophe. Professional editors often specifically flag "its" and "it's" for a final pass on any document, since the error is easy to make even for experienced writers working quickly, and spell-checkers alone won't catch it because both spellings are valid words in isolation — only context tells you which one a given sentence needs. Editors sometimes recommend a targeted find-and-check pass specifically for "its" and "it's" in any document longer than a page or two, since the eye tends to glide past the error during normal reading.
Examples with “its”
- The company changed its logo last year.
- The cat licked its paw clean.
- Every rule has its exception.
- The team celebrated its first win of the season.
- The tree lost most of its leaves in the storm.
- The book is missing its final chapter.
- The car needs its oil changed soon.
- The museum expanded its collection this year.
Examples with “it's”
- It's already past midnight.
- It's been a while since we last spoke.
- I think it's going to rain later.
- It's clear that the plan needs revising.
- It's the best decision we've made all year.
- It's not too late to change your mind.
- It's obvious she worked hard on this.
- It's rare to see snow this early in the season.
Memory trick
Say the sentence out loud with "it is" substituted in — if it still sounds natural ("it is raining"), the apostrophe version is correct; if it sounds wrong ("the dog wagged it is tail"), you need the possessive "its" with no apostrophe. Grammar-checking software today catches this pair reasonably reliably by scanning sentence structure, but it wasn't always so: for decades, this error slipped past basic spell-checkers entirely, since both "its" and "it's" are individually correct words, and only full-sentence context can tell which one a given spot actually needs. A quick final gut-check: if removing the word and reading the bare sentence still leaves a grammatically complete thought without it, you likely have a contraction rather than a required possessive modifier.