Text Compare & Difference Checker
Compare two versions of code, contracts, or plain text side-by-side. Spot exact line additions, removals, and character-level edits instantly with complete client-side confidentiality.
Paste two versions of your text above and click "Compare Difference" or to see line-by-line and character-level highlights.
How the LCS Dynamic Programming Diff Algorithm Works
Text comparison algorithms determine the minimal sequence of insertions and deletions necessary to convert string A into string B. This implementation utilizes a matrix-based dynamic programming solution to find the Longest Common Subsequence (LCS):
The LCS Recurrence Relation
LCS(i, j) = LCS(i-1, j-1) + 1, if A[i-1] == B[j-1]
LCS(i, j) = max(LCS(i-1, j), LCS(i, j-1)), otherwise
Once the 2D cost matrix is populated, a backtracking traversal from index (n, m) to (0, 0) extracts the optimal diff path with time complexity O(n × m).
Side-by-Side Review
Dual-column alignment synchronizes modified lines directly across from their original counterparts, rendering intuitive visual redlines.
Intra-Line Character Highlights
When a line is modified rather than fully deleted, intra-line LCS flags the exact characters and words altered within the line.
100% Client-Side Privacy
Safe for proprietary source code, confidential NDA agreements, credentials, and environment configuration variables.
Frequently Asked Questions
How do I compare two strings online with this tool?
Paste your first string into the 'Original Text' column on the left and your second string into the 'Modified Text' column on the right. Our in-browser diff engine immediately calculates additions, removals, and intra-line character changes, highlighting modified tokens in green and red with zero delay.
How does this online text and string compare tool work?
Our diff engine uses the Longest Common Subsequence (LCS) dynamic programming algorithm. It breaks both input texts into lines, identifies added, removed, and unchanged blocks, and then performs secondary intra-line character-level LCS analysis on modified line pairs to highlight the exact edits within lines.
Is my text, code snippet, or string sent to any server?
No. The entire diff calculation executes locally inside your web browser's JavaScript engine. No text strings, filenames, or metrics are uploaded or transmitted to any remote server or third-party service.
What is the difference between Line Diff and Word Diff?
Line Diff compares documents line by line in a dual-column layout, which is optimal for programming code, config files, and JSON payloads. Word Diff tokenizes text by words and whitespace, rendering an inline single-pane view that is ideal for prose, articles, and contractual redline revisions.
Can I compare code snippets or JSON strings side-by-side?
Yes. Line Diff mode preserves indentation, syntax structure, and newline formatting, making it ideal for checking git commit differences, config files (YAML, JSON, XML), or Python and TypeScript snippets.
Can I export the differences as a Git patch file?
Yes. Clicking 'Download .patch' generates a standard unified diff format (.patch) file compatible with Git apply, patch(1), and common CI/CD inspection tools.
What does 'Ignore Whitespace' do?
When enabled, differences caused strictly by trailing spaces, multiple consecutive tabs, or newline differences (CRLF vs LF) are normalized, allowing you to focus exclusively on meaningful substantive content edits.