What actually changed
Paste two versions and every difference is marked where it sits — word by word, not line by line. Everything that survived is left plain, which is usually the part you were checking.
Checking what an AI tool did to your draft? Put the version you checked on the left and what came back on the right. Changed numbers, dropped qualifiers and new deadlines are listed first.
Paste both versions. Everything that changed is marked in place — removed text struck through, new text underlined — and everything that survived is left plain.
Checking an AI rewrite
An AI tool asked to make writing “clearer” rewrites all of it, and the changes that matter are small: “around 1100” becomes “at 1100”, “not confirmed” disappears, a letter gains “within five business days”, a citation's page number moves. The rewrite reads better, which is why nobody looks twice.
- Left box: the version you wrote or checked. For a brief, the cite-checked draft.
- Right box: exactly what the AI tool returned, before you change anything.
- Read “Facts to check” first. It lists numbers, times and dates that appear a different number of times, qualifiers such as “around”, “appears” and “not confirmed” that were dropped or added, and new firm wording such as “within”, “immediately” or “must”.
- Then read every marked change. The list is a word count: it can tell that “not confirmed” went, not which fact the doubt now sits on. A paragraph turned into bullet points is compared word by word, so only the words that changed are marked.
Why this matters: how an AI edit changed checked citations in a Connecticut case, and a worked example in the incident report template. Nothing you paste here is uploaded.
Word by word, not line by line
Most comparison tools work a line at a time. Change one word in a paragraph and the whole paragraph turns red, then green — technically correct, and useless, because you still have to read both versions to find the word.
This compares lines first to work out which ones survived, then compares the words inside the ones that were rewritten. So a clause where thirty (30) days became forty-five (45) days shows you those two changes and leaves the other forty words alone.
What people check with it
A contract that came back
They said they made two small changes. This tells you whether that is true, and where.
A draft after an AI edit
Paste what you checked and what the AI tool gave back. Numbers, qualifiers and new deadlines are listed first; every other change is marked in place.
Two exports that should match
Two lists that ought to be identical and are not. The Two lists button gives you the three answers: only in A, only in B, in both.
A policy or terms update
Published documents change quietly. Keep the old one and you can always see exactly what moved.
Comparing lists? Tidy them first
Two lists rarely differ only in their contents. One has trailing spaces, one has blank lines, one is sorted and the other is not — and the comparison reports differences that are not really differences.
Run both through the list cleaner first — trim, deduplicate, sort — then paste them here. The two tools are built to be used one after the other.
What it does not do
It compares words, not formatting. You can open a Word document, a PDF or a text file on either side, and it is read in your browser rather than uploaded, but only the words come across: bold, headings, tables and tracked changes are not compared. A scanned PDF has no words to read. When the formatting matters too, Word's own Compare Documents is the right tool.
It also has a ceiling: three thousand lines a side. Past that, the comparison needs more memory than a phone has, and the tool says so rather than freezing. The Two lists button above has no line limit, because comparing lists doesn't need the word-by-word table.
If what you want is not the difference between two versions but a better version of one, the cliché finder marks what is worth cutting, and the readability checker scores how hard it is to read.
More free tools
Most of these run entirely in your browser; the citation tools check references against public databases.
Word Counter
Words, characters, sentences and reading time, live.
Citation Checker
Check references and case citations are real.
Spot the Change
A daily game: find what a rewrite changed.
Daily Crossword
A newspaper-style crossword, new every day.
Case Converter
Switch text to UPPER, lower, Title or Sentence case.
Word Cloud
Your most-used words, drawn bigger.
Readability
How easy your writing is to read, as a school grade.
Word Unscrambler
Type some letters, get every word they make.
Reading Time
How long a piece takes to read.
Citation Generator
Format a source for a reference list: APA, MLA, Chicago or Harvard.
Essay Counter
Word goals and progress for longer drafts.
X / Twitter Counter
Check a post fits before you publish it.
Instagram Counter
See where your caption gets cut off.