Text Diff Checker
Paste two versions of a text and see exactly what changed — added and removed lines, with the changed words inside each line highlighted. View side by side or inline, ignore case or whitespace, and export the result as a standard unified diff.
How the Diff Checker Works
It finds the smallest set of added and removed lines that turns the original into the changed text — the same idea behind git diff.
Both texts are split into lines and compared with the Myers diff algorithm, which finds a minimal edit script: every line is either unchanged, removed from the original, or added in the changed version. When a removed line is immediately replaced by an added one, the pair is shown as a modified line, and a second, word-level diff highlights exactly which words changed.
Ignore case and Ignore whitespace make the comparison forgiving — useful for re-indented code, text pasted from different editors, or capitalisation fixes you don't care about.
Side by side shows the two versions in parallel columns; Inline shows a single column with removals above additions, like a code review. On small screens Inline is chosen automatically. Long runs of unchanged lines are collapsed into folds you can expand, so you can jump straight to what changed.
Copy diff and Download .diff export the changes in the standard unified diff format (@@ -12,7 +12,8 @@ hunks with three lines of context), which works with patch, git apply and code review tools.
What the Colours and Symbols Mean
The same markers are used on screen and in the exported unified diff.
Removed
Red lines exist only in the original. In a .diff file they start with -.
Added
Green lines exist only in the changed text. In a .diff file they start with +.
Modified
A removed line next to an added one. The darker highlight marks the words that actually changed.
Hunk header
@@ -12,7 +12,8 @@ means: 7 lines from line 12 of the original became 8 lines from line 12 of the changed text.
How to Use the Text Diff Checker
Get your result in under ten seconds.
Paste or drop both versions
Original on the left, changed on the right. Text files can be opened or dropped onto either side.
Read the differences
The diff updates as you type. Switch between side by side and inline, expand collapsed sections, and toggle ignore options.
Export if needed
Copy or download the changes as a unified .diff file for git, patch or a code review.
Why Use the Text Diff Checker on Developers Web Tools
Fast, accurate and private — built for developers.
Minimal, accurate diff
Myers algorithm — the fewest possible added and removed lines, like git.
Word-level highlights
See exactly which words changed inside each modified line.
Works on any screen
Side by side on desktop, inline on phones, with wrapping or sideways scrolling.
Ignore the noise
Skip case and whitespace differences such as re-indentation.
Fast on big files
Background processing, collapsed unchanged lines and incremental rendering keep 100k-line files smooth.
Private
Both texts stay in your browser — safe for contracts, code and configs.
Frequently Asked Questions
Paste the original version into the left box and the changed version into the right box. The differences appear below automatically: red for removed lines, green for added lines, with changed words highlighted.
Yes. Click Open file above either box, or drag and drop a file onto it. Any plain-text format works — .txt, .csv, .md, .json, .html, source code and more — up to 50 MB each.
Lines that differ only in the amount of spaces or tabs, or in leading and trailing whitespace, are treated as unchanged. This is useful for re-indented code or text copied from different editors. Unchanged lines are shown as they appear in the original.
A standard text format for describing changes, used by git, diff -u and patch. It lists hunks of changed lines with three lines of context; removed lines start with - and added lines with +. Use Copy diff or Download .diff to export it.
The comparison works line by line, and a paragraph without line breaks is one long line. Keep Highlight changed words on — the exact words that changed are highlighted inside it.
Files up to 50 MB each can be loaded; texts over 256 KB are compared in a background thread so the page stays responsive. Results are rendered in chunks (use “Show more” at the bottom), and unchanged sections are collapsed by default. For extremely different large files the diff may be simplified for speed, which is noted below the result.
No. The comparison runs entirely in your browser; nothing is sent to a server.