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🔍 Text Diff Checker

Compare two blocks of text — see added, removed, and unchanged lines with word-level highlights. Runs entirely in your browser.

Original0 lines
Modified0 lines
Diff +0 added −0 removed 0 unchanged
Paste text on both sides and the diff appears here live.
Copied to clipboard

About Text Diff Checker

Text Diff Checker is a free browser-based tool for comparing two blocks of text and seeing every difference between them, line by line. Paste your two versions, and the diff renders live — green for what was added, red for what was removed, with optional word-level highlights inside each changed line.

It works on anything text-based: code, config files, articles, contracts, meeting notes, JSON, YAML, CSV rows. If you can copy-paste it, we can diff it.

Under the hood we use a Longest Common Subsequence (LCS) algorithm — the same approach behind git diff, VS Code's built-in diff view, and every serious diff tool. It correctly handles insertions, deletions, and moved lines without getting confused.

100% client-side: The diff is computed in your browser via pure JavaScript. Nothing you paste is uploaded — safe for confidential contracts, unpublished code, or private notes.

How to use Text Diff Checker

1

Paste two versions

Drop your original text on the left and the modified version on the right. Or hit Load sample to try it first.

2

Pick your view

Side-by-side shows old and new columns. Unified shows one column with +/− markers (Git-patch style).

3

Copy or Download

Copy the patch to your clipboard or Download as a .patch file compatible with git apply and patch.

Key Features

Live diff as you type

Every keystroke recomputes the diff. See changes instantly, no button to click.

Side-by-side + Unified views

Side-by-side shows original vs modified in two columns — best for skimming. Unified inlines both with +/− prefixes — best for patch review or copying to a Git commit.

Word-level highlights

Inside changed lines, we highlight the specific words that differ — so you see exactly what changed, not just that the line changed.

Ignore options

Toggle to ignore whitespace (great for reformatted code), ignore case (useful for content changes), or skip blank lines. Options apply live.

Live stats

Status bar shows added, removed, and unchanged line counts — a quick overview before diving into details.

Copy or download as .patch

Export the diff in unified format compatible with git apply, patch -p1, or any diff tool. Perfect for sharing changes without the full files.

Swap sides

One click flips original and modified — useful when you realize you pasted the wrong version first.

Common Use Cases

  • Review a code change before applying it — spot every added/removed line
  • Compare two contract versions to see what a counterparty edited
  • Diff a config file after a package update to spot breaking defaults
  • Check for content changes between two versions of an article or blog draft
  • Compare two API responses to find what changed between calls
  • Verify a translation matches the source structure line-for-line
  • Debug why two files that "look the same" actually differ (whitespace, invisible chars)
  • Generate a patch file to send to a colleague without giving them the whole file

Security & Privacy

  • 100% client-side: the diff is computed in your browser. No content is ever uploaded to our servers.
  • Works offline: once the page loads, you can disconnect and it still works.
  • No content logging: we don't see or store what you paste. There's nothing for us to see.
  • No accounts required: fully anonymous. Use it as often as you want.
  • Standards-only JavaScript: no third-party diff library — just a small LCS implementation.

Frequently Asked Questions

No. The diff runs entirely in your browser. Safe for confidential contracts, unpublished code, or private notes.
Longest Common Subsequence (LCS) with dynamic programming for line-level diff, and a similar approach for word-level highlights within changed lines. Same family of algorithms Git and VS Code use.
Up to about 10,000 lines per side comfortably. Beyond that, the LCS dynamic programming table grows to O(n×m) and can slow the browser. For 100K+ line files, use a native tool like diff or git diff.
Yes. Download the .patch and apply it with git apply patch.patch or patch -p1 < patch.patch. It's in the standard unified diff format.
Auto-formatters (Prettier, Black, gofmt) often reflow whitespace without changing behavior. Enabling "ignore whitespace" hides those noise changes so you see only real edits.
Yes. Completely free, no signup, no ads.