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Text Diff Checker

Paste two versions of some copy, code or config and see exactly what changed, down to the word, side by side or in one column.

Text Diff Checker at a glanceIllustration: 1, Two versions; 2, processed in your browser; 3, What changed.Text Diff Checker1Two versions−++3What changed2In yourbrowser
1 Two versions 2 processed on your device 3 What changed

Text Diff Checker

Original

Changed

Differences

Unified diff (.patch)

01

What it does

Compares two texts line by line with word-level highlights, side by side or inline, and makes a .patch file.

  • Line-by-line comparison (LCS)
  • Changed words highlighted within lines
  • Inline or side-by-side view
  • Ignore trailing spaces or case

02

Private by design

Everything happens in your browser. Nothing you type, paste or upload is sent anywhere, and it keeps working offline once the page has loaded.

03

What you get

A highlighted comparison and a unified diff, with a Copy and a Download button on every result.

  • Diff
  • Compare
  • Patch

Why it matters

'What did the client change?' comes up constantly: revised copy, an edited config file, two versions of a contract page. Reading both versions side by side misses small changes, such as one digit in a phone number.

A diff shows every added, removed and changed line, and highlights the exact words that changed. Unlike many online diff sites, nothing you paste leaves your browser.

How it works

  1. InputOriginal and changed text
  2. In your browserMyers line diff, then word highlights
  3. OutputInline or side-by-side view and a unified .diff

Where it fits in a designer's workflow

  1. Plan
  2. Design
  3. Build
  4. Test
  5. Launch
Checking copy and config changes before they go live.

By the numbers

What the diff finds in the sample opening hoursUnchanged lines: 3; Changed: 2; Added: 1; Removed: 0Unchanged lines3Changed2Added1Removed0
Computed with this tool's own Myers diff, the same algorithm git uses by default: it finds the fewest lines to add and remove, then pairs removed and added lines as changes and highlights the words that differ. Source: Myers (1986) An O(ND) difference algorithm.
Show the numbers as a table
KindLines
Unchanged lines3
Changed2
Added1
Removed0

How to use it

  1. Paste the original on the left and the changed version on the right.
  2. Choose one column or side by side.
  3. Read the summary and scroll the highlighted changes.
  4. Download the unified diff if you need a patch file.

FAQ

How does it decide what changed?

It finds the longest common sequence of lines, the same idea git uses, then compares the words inside changed lines.

Can it compare Word documents?

Paste the text from them. It compares plain text, not formatting.

How big can the texts be?

A few thousand lines each is quick. Very large files may take a moment.

Is the text private?

Yes. The comparison runs entirely in your browser.

Work with me

Want a site that gets these right?

I build fast, accessible websites and web apps that pass these checks from day one. Tell me about your project and I'll reply personally with honest next steps.

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