About

In strict development environments, sending proprietary code to external servers for comparison is a security violation. This tool operates exclusively within your browser's Local Runtime Environment, ensuring that sensitive configuration files, API keys, and algorithms never traverse the network. It bridges the gap between desktop IDEs and web utilities by offering granular, character-level difference detection.

Accuracy in code review dictates that identical data structures should be treated as equal, regardless of formatting. Unlike standard string comparators, this utility includes intelligent pre-processors: it can prettify minified JavaScript, sort JSON keys alphabetically, and normalize XML structures before performing the diff. This eliminates false positives caused by linter rules or serialization discrepancies.

Formulas

The comparison engine utilizes the Myers algorithm to compute the Shortest Edit Script (SES). The goal is to maximize the number of matching items in the trace. The edit distance D is defined as:

D = N + M - 2 × LCS(A, B)

Where N and M are the lengths of the sequences. To determine similarity percentage S, we calculate:

S = 2 × MatchesLength_A + Length_B × 100%

For character-level precision inside modified lines, a secondary Levenshtein distance calculation is performed on the specific substrings.

Reference Data

Diff Type	Visual Indicator	Algorithmic Cost	Use Case
Identity	= Grey	O(1)	Unchanged code blocks
Insertion	+ Green (Bg)	O(N)	New features, added logic
Deletion	− Red (Bg)	O(N)	Deprecated code removal
Mutation	Δ Yellow/Blue	O(M×N)	Variable rename, typo fix
Whitespace	Dimmed	NULL	Indentation fixes (Tabs vs Spaces)
Move	Arrow →	Heuristic	Function reordering
Conflict	! Striped	Manual	Merge conflicts (HEAD vs Incoming)

Frequently Asked Questions

Yes. Comparing minified files (single long lines) is notoriously difficult. Use the "Prettify/Format" button in the toolbar before running the diff. This expands the code into a readable structure, allowing you to identify logic changes rather than just seeing one giant red line and one giant green line.

Standard diff tools mark this as a total change. Our tool includes a "Sort JSON" feature. This recursively organizes all keys alphabetically before comparison, ensuring that { "a": 1, "b": 2 } is treated as identical to { "b": 2, "a": 1 }.

By default, yes. "Function" and "function" are treated as different. However, you can toggle "Ignore Case" in the settings if you are working with languages like SQL or old BASIC variants where capitalization does not affect execution.

We utilize HTML5 Web Workers to offload the heavy computational logic (the O(ND) algorithm) to a background thread. This keeps the UI responsive, allowing you to scroll and interact with settings even while a 50,000-line comparison is being calculated.