Code Diff Checker

Compare two code files side by side — syntax-highlighted diff with line-level precision

What Is a Code Diff Checker?

A code diff checker compares two versions of source code and highlights every difference — added lines, removed lines, modified lines, and within modified lines, the specific characters that changed. Unlike plain text diff tools, a code-aware diff applies syntax highlighting to the source files, making it easy to read the code context around each change. The side-by-side view shows the original and modified versions aligned for visual comparison.

Code diff checking is fundamental to software development: reviewing pull requests, debugging regressions by comparing working and broken versions, verifying that code generation produces expected output, auditing configuration changes, and understanding what a refactoring actually modified. A good diff tool distinguishes between meaningful changes and cosmetic reformatting, helping developers focus on the substance of each modification.

How to Compare Code Files

1. Paste the original code into the left editor panel
2. Paste the modified code into the right editor panel
3. The diff computes automatically, highlighting changes in both panels
4. Green highlighting shows additions, red shows deletions, yellow shows modifications
5. Within modified lines, word-level changes are highlighted for precise identification

Why Use PinusX Code Diff Checker?

PinusX compares your code with 100% client-side processing. Both code versions stay in your browser — nothing is uploaded to any server. This is essential when diffing proprietary source code, unreleased features, security-sensitive configurations, or internal codebases that must not be exposed. In November 2025, jsonformatter.org leaked over 80,000 user credentials from server-side processing. PinusX prevents code exposure by running the entire diff algorithm and syntax highlighting locally in your browser tab using JavaScript.

Frequently Asked Questions

What programming languages are supported?

The diff checker supports all major programming languages for syntax highlighting: JavaScript, TypeScript, Python, Java, Go, Rust, C, C++, Ruby, PHP, Swift, Kotlin, SQL, HTML, CSS, YAML, JSON, Markdown, Shell/Bash, and many more. Language detection is automatic based on code patterns, or you can manually select the language.

Does it show word-level differences?

Yes. Within modified lines, the checker highlights the specific words or characters that changed, not just the entire line. This is especially useful when a line has a small change (like a variable name or number) — you can immediately see exactly what was modified without comparing the full lines character by character.

Can I compare code from different languages?

You can paste any two pieces of text regardless of language. The diff algorithm works on text content and does not require both sides to be the same language. This is useful for comparing templates, generated output against expected output, or translated code between languages.

How does it handle whitespace differences?

By default, the checker shows all changes including whitespace. You can toggle a setting to ignore whitespace differences (leading indentation, trailing spaces, blank lines) so the diff only shows substantive code changes. This is useful when comparing code that was reformatted or uses different indentation styles.

Your data never leaves your browser. 100% client-side processing.