Compare Code Online — Syntax-Aware AST Diff
Compare two versions of source code side by side with our free code diff checker. Powered by WebAssembly Tree-sitter parsers to separate refactors and renames from real logic changes. 100% private in-browser execution.
Built for Developers Refactoring Real Codebases
Standard line-by-line diffs flood you with noise when variables are renamed or methods are reordered. Our Tree-sitter AST code diff checker understands syntax structure so you focus on actual logic changes.
100% In-Browser Privacy
Proprietary source code, API keys, and internal algorithms never leave your device. All AST parsing and diff computations run locally in WebAssembly.
AST Syntax-Aware Parsing
Parses JavaScript, TypeScript, Python, JSON, HTML, and CSS into abstract syntax trees to distinguish meaningful statements from whitespace and formatting.
Renamed Variable & Identifier Matching
Dual-hash matching recognizes when a function, parameter, or variable was renamed consistently across a scope, displaying it as a rename rather than a full rewrite.
Moved Function & Block Detection
Methods or classes reordered within a file are linked with visual moved indicators instead of appearing as a deletion in one place and an addition in another.
Interactive Side-by-Side Merge
Selectively accept or reject individual edits, test resolutions in place, and copy the unified code directly to your clipboard or editor.
How to Compare Two Code Files in Seconds
Paste or Drop Source Files
Paste your original code on the left and the updated version on the right, or drop source files directly into either panel.
Inspect Structural Differences
Review syntax-highlighted additions, deletions, renames, and moved blocks with similarity metrics and word-level accuracy.
Merge and Copy the Clean Output
Apply individual revisions between panels with one click or copy the resolved code back into your repository or IDE.
Why Use Our Online Code Diff Checker for Software Development?
Tree-sitter AST code comparison vs. naive line-by-line diffs
Standard text diff tools (and standard git diff) treat source code as flat lines of ASCII characters. When an engineer reformats code with Prettier or Black, indents a function inside an if block, or alters trailing commas, a line diff highlights the entire block as deleted and rewritten.
Text Compare Tool compiles WebAssembly Tree-sitter parsers directly in your browser. By constructing concrete syntax trees for JavaScript, TypeScript, Python, JSON, HTML, and CSS, it analyzes language tokens and structural nodes. You immediately see whether a commit changed program semantics or merely touched syntax.
Code diff checker for multi-language development: Python, JS, TS, HTML, and SQL
Modern web applications span multiple layers: frontend components (TypeScript, JSX, Vue, HTML, CSS), backend microservices (Python, Go, Node.js), and database queries (SQL DDL and migration scripts). Our code diff checker adapts to each language.
For frontend developers, it works as an HTML diff checker and CSS diff tool to spot altered attributes or changed styles. For backend engineers, it highlights logic branches, imported modules, and altered database queries without tripping on indentation or formatting differences.
Identifier normalization: Catch renames without the noise
A common refactoring task is renaming an ambiguous variable (like changing data to userProfile). In line-oriented diff engines, every occurrence is marked as a code change, obscuring genuine bug fixes nestled inside the same diff.
Our structural engine calculates a dual hash for every syntax unit: a literal hash and an identifier-normalized hash. When the structure and keywords match but variable names differ consistently, the tool recognizes the rename and scores it with high similarity rather than treating it as alien code.
Moved function and block detection in complex refactors
When reordering functions, organizing methods alphabetically, or extracting helper classes into new positions, classic line diffs produce an overwhelming wall of red deletions and green additions. Our engine identifies that the code block was relocated intact, tagging it with a moved badge and origin reference.
Zero cloud exposure for proprietary source code and git diffs
Pasting proprietary algorithms, backend services, or unreleased features into third-party cloud diff checkers exposes intellectual property and risks compliance breaches under corporate security policies and SOC 2 guidelines.
Text Compare Tool is completely client-side. The grammars, diff algorithms, and editor buffers execute inside your browser sandbox using WebAssembly and Web Workers. No source code or token ever touches our servers or third-party APIs.
Frequently Asked Questions About Online Code Comparison
Which programming languages are supported for AST syntax diffing?
The structural engine includes precompiled WebAssembly Tree-sitter grammars for JavaScript, TypeScript, TSX, Python, JSON, CSS, and HTML. All other languages (including SQL, Go, Rust, C++, Java, PHP) and plain text are compared using our high-speed strict line-and-character engine.
Can I use this as an online code diff checker for Git pull requests?
Yes. You can paste the contents of files before and after a commit or pull request, or drop individual source code files directly into the panels to inspect differences side by side with word-level and syntax-level precision.
Is my proprietary source code uploaded or stored on any server?
No. Zero bytes of your source code are uploaded to any server. The Tree-sitter parsers and diff calculation algorithms run entirely client-side in your browser via WebAssembly and Web Workers.
How does the code diff checker handle renamed variables and functions?
The engine uses dual hashing (literal and identifier-normalized hashes). If a block has the same AST structure and keywords but identifiers were renamed, it identifies the pattern as a structural match rather than a complete rewrite.
Can I resolve merge conflicts or selectively apply code changes?
Yes. You can click the merge arrows beside any diff block to copy changes from one version to another, and edit the code directly in either editor panel before copying the final result.
How does moved function detection work in code files?
When a function or class is relocated to a different place in the file, the engine detects the matching AST structure and flags it with a moved badge showing its origin line, rather than marking it as deleted and added anew.
Want to understand the inner workings of AST code diffing?
Explore how tree-sitter concrete syntax trees, dual hashing, and moved-block heuristics separate real logic changes from refactors.