Text Diff & Code Comparison Tool

How This Tool Works

Operation: The Text Diff Tool compares two text inputs line-by-line using an implementation of the Longest Common Subsequence (LCS) algorithm, which is the standard approach used by version control systems like Git. The algorithm works as follows: it builds a two-dimensional matrix representing all possible character/line sequences between the two texts, then traces back through the matrix to find the longest sequence that appears in both inputs. Lines present in the left input but not the right are marked as deletions (highlighted in red). Lines present in the right input but not the left are marked as additions (highlighted in green). Lines common to both are displayed normally. The output is rendered as a unified diff view, with each line prefixed by a +, -, or space character following the standard unified diff format convention.

Character-level diffing: When a line differs, the tool also performs a character-level comparison within that line to highlight exact character insertions and deletions, providing pixel-level precision.

Key Benefits of Using the Text Diff

• Total data confidentiality: Paste proprietary source code, confidential legal documents, or internal business text without risk. Every comparison runs locally — your two documents never leave your device, making this safe for IP-sensitive material.
• Line and character granularity: The tool provides both line-level and character-level diff highlighting. Changed lines are marked holistically, and within changed lines, individual inserted/deleted characters are also highlighted for surgical precision.
• Side-by-side output clarity: The unified diff view uses clear colour coding (red for removed, green for added) with line numbers on both sides, making it easy to scan through even large documents and identify exactly what changed.

Practical Real-World Use Cases

• Software engineers reviewing code changes: A developer comparing two versions of a JavaScript function to identify exactly which lines were added, removed, or modified can use character-level highlighting to spot a single semicolon change or variable rename within a larger block.
• Writers tracking document revisions: An editor comparing a draft article with the client's revised version can instantly see every changed sentence and word, ensuring no requested edits are missed during the final proofreading pass.
• Students verifying plagiarism or originality: A student comparing their essay draft with a final submission can verify that all intended edits were applied correctly and that no accidental content was duplicated or omitted.

Frequently Asked Questions (FAQ)

What is the maximum text size supported?

The tool can handle documents up to approximately 100,000 characters per side before browser performance degrades noticeably. The LCS algorithm has O(n×m) complexity, so very large documents may take a few seconds to process.

Can I compare PDF or Word files directly?

No — the tool compares plain text only. To compare Word documents or PDFs, copy and paste the extracted text content into both input panels. The character-level diff will still highlight changes accurately.

Does this tool support ignoring whitespace differences?

The current version performs exact character-level comparison including whitespace. For code comparison, trailing whitespace differences will be highlighted. Consider trimming both inputs before pasting if whitespace changes are irrelevant.