Diff Checker
Compare two texts or code snippets side by side and highlight the differences with LCS-based diffing.
Diff Checker
Compare two texts or code snippets and highlight the differences
Options
Paste two texts above and click "Compare" to see the differences
What is a Diff Checker?
A diff checker is a tool that compares two pieces of text or code and highlights the differences between them. Developers use diff tools daily to review code changes, compare configuration files, and understand what changed between two versions of a document.
CodeHelper's Diff Checker uses an LCS (Longest Common Subsequence) algorithm to produce accurate diffs with line-level granularity, supporting both unified and side-by-side views.
Key Features
- Unified View: See additions and removals in a single stream with +/- prefixes and color coding.
- Side-by-Side View: Compare original and modified texts in parallel columns.
- Ignore Options: Optionally ignore leading/trailing whitespace or case differences.
- Statistics: See how many lines were added, removed, and unchanged.
- Swap Inputs: Quickly reverse the comparison direction.
How to use the Diff Checker
- Paste the original text in the left panel.
- Paste the modified text in the right panel.
- Click Compare to see the differences.
- Toggle between unified and side-by-side views.
- Copy the diff output for documentation or code review.
Common diff checker use cases
- JSON diff: Compare two API responses side by side to find changes between versions.
- Config file comparison: Compare .env, nginx.conf, or YAML configuration files before and after a change.
- Code review: Paste two versions of a function to review what changed without opening a full git client.
- SQL query diff: Compare two versions of a query to understand optimization changes.
- Documentation comparison: Find differences between two versions of a README or specification document.
Whether you are reviewing pull requests, comparing API responses, or tracking configuration changes, this free diff checker makes differences instantly visible.
Frequently Asked Questions
How do I compare two texts online?
Paste the original text in the left panel and the modified text in the right panel, then click Compare. Added, removed and changed lines are highlighted, and you can switch between side by side and unified views. It works for plain text, code, JSON, YAML, SQL and configuration files.
Is it safe to paste code or confidential text into an online diff checker?
It depends on the tool. This diff checker runs entirely in your browser: the texts you paste are never uploaded, stored or logged on any server, so it is safe for proprietary code, configuration files and documents. With server side comparison tools, treat anything you paste as shared with that service.
What algorithm does the diff checker use?
It uses LCS (Longest Common Subsequence) diffing, the same family of algorithms behind git diff. LCS finds the largest block of unchanged content between the two versions and marks everything else as additions or deletions, which produces minimal, readable diffs.
What is the difference between a unified diff and a side by side diff?
A side by side diff shows the two versions in parallel columns, which is easiest for visual review. A unified diff interleaves changes in a single column with + and - prefixes, the format used by git and patch files. This tool supports both views on the same comparison.
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