Diff Checker
Every Added, Removed and Edited Line, Highlighted
This diff checker works online, comparing two texts and marking every difference between them. First, paste the old version and the new one. Then read what moved, because both texts stay inside this tab.
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Diff Checker
Paste two versions — every line that arrived, left or changed gets marked
- Lines added
- 0
- Lines removed
- 0
- Lines changed
- 0
- Match
- 0%
What changed
- Paste a text into each panel and the differences appear here.
Ready. Paste both versions and the marks appear below.
What a Diff Checker Shows You That Your Eyes Miss
A diff checker lays two drafts side by side and marks each edit. Lines that match stay plain, lines that appeared turn one colour, and lines that vanished turn another.
The idea started with programmers comparing code. Programmers needed a fast way to see what one edit did to a file, so they built tools that show changes rather than describe them. Today the same idea serves writers, editors and anyone comparing a contract.
This one works on plain text. Paste any two versions and you get an honest view of the gap between them, with counts that tell you how large that gap is.
Underneath, every diff tool solves one classic puzzle. It is the longest common subsequence problem, and the shape of it explains the odd results.
Situations That Call for a Text Comparison
Proofreading is the common case. A writer sends a revision and the editor wants to know what moved, so a text compare saves reading the whole piece twice looking for the change.
Review sits close behind. Two versions of a policy, a price list or a set of terms can differ by one line that matters, and a careful eye catches that line where a skim does not.
Line Mode and Word Mode
Line mode suits code, lists and anything built from separate rows. It tells you which lines arrived and which left, and it stays readable on a long file.
Word mode suits prose. When one sentence changes three words in the middle, marking the whole line as changed is noise. Word mode narrows the highlight to the words that actually differ.
Why Whitespace Changes Are Worth Seeing
A missing space or a stray tab looks tiny and matters often. An ignore-whitespace option hides those rows, so you can focus on real edits and check spacing separately.
Four Steps to Compare Two Versions of a Text
The Denwix diff needs no account and no file upload. Both texts stay on your own machine, so the comparison finishes in a blink.
- 1
Paste the original
Drop the first version into the left panel, exactly as it stands. The diff updates while you type.
- 2
Paste the revision
Put the second version beside it. Then pick line mode for code and lists, or word mode for prose.
- 3
Read the marks
Added lines, removed lines and changed words each carry their own colour, so the shape of the edit shows up at a glance.
- 4
Copy or download
One button copies the report, another saves a file. Meanwhile both drafts stay on your own machine.
A Text Compare Built for Real Drafts
A simple equals check tells you two texts differ. This one tells you where, and by how much.
Two comparison modes
Line mode for lists and code, word mode for sentences. Every view tells you something different about the two drafts.
Colour you can see
Every mark carries a label as well as a colour, so the report stays readable in bright light and for colour-blind readers.
Whitespace control
Ignore spaces and tabs when they do not matter, or switch the check back on when they do.
Change counts
Added, removed and changed totals appear above the report, so you know the size of the edit before you read it.
Swap in one click
Put the newer version first when you want to read the changes the other way round. No retyping either panel.
Nothing leaves your tab
Your browser compares the two texts. There is no request, no storage and no log, so private drafts stay private.
Getting a Useful Comparison
These six habits keep the report short and the answer obvious.
- Compare like with like. Both panels should hold the same kind of content. Line mode on a paragraph of prose gives you noise.
- Settle the whitespace question first. Decide whether spacing counts. That single choice changes the whole report, so make it before you read.
- Read the counts before the detail. A change count of three lines is a quick check. A count of two hundred means you compare two different drafts.
- Keep both versions. The report shows the difference, not the full text. Therefore hold onto your sources until the review closes.
- Use word mode for editing. Line mode flags a whole sentence when one word moved. Word mode points at the word, which saves a slow read.
- Compare the exact copy that goes live. A last compare against the published copy catches the change somebody made after the review finished.
Diff Mistakes That Hide a Change
Each one turns a clear report into a wall of noise.
Line mode on flowing prose
One comma marks a whole paragraph as changed. Switch to word mode and the real edit appears.
Pasting a reformatted file
An editor that rewrapped every line hides the one line that mattered. Compare the source, not the export.
Ignoring whitespace too early
A missing space can break a link or a template. Check spacing once before you hide it.
Diff Checker FAQ
What does a diff checker actually compare?
It compares two texts character by character, then groups the differences into runs it can show. Lines that match stay plain, while added and removed runs take their own colour. The result reads as a map of the edit rather than two walls of text.
Should I use line mode or word mode?
Line mode for anything built from separate rows, which means code, config files and lists. Word mode for prose, because a single changed word should not mark a whole sentence. When in doubt on a document, start with word mode.
Can the tool ignore whitespace?
Yes, and the option stays off by default so nothing hides without you asking. Switch it on and the comparison skips differences in spaces, tabs and line endings, which suits code where indentation carries no meaning.
Does the text I paste here ever reach a Denwix server?
No. The comparison runs in your browser on your own device, so there is no request, no storage and no log. Contracts, drafts and unpublished copy stay on your machine, and the tool works with no connection at all.
Does it compare more than two files?
Two at a time. A two-way comparison answers the question most people arrive with, which is what changed between the version I had and the version I have. For a three-way merge, reach for a version control tool.
How big can each text be before the Denwix diff slows down?
Comfortably into the tens of thousands of lines, since the browser holds everything in memory. Very large files slow the first paint rather than failing, so split anything enormous into sections and compare those.
More Denwix Tools Worth Opening Next
Every Denwix tool listed here runs locally, with no login and nothing uploaded.
Duplicate Line Remover
Remove repeated rows and keep the first copy of each.
Open tool →Case Converter
Swap your text between capitals, small letters, title style and sentence style with one click.
Open tool →Word Counter
Tallies for words, letters, sentences and minutes of reading, refreshed on every keystroke.
Open tool →
Spot the edited line almost instantly
Paste both versions, pick a mode, and read what moved. Nothing travels anywhere and nothing sticks around.