Diff Checker
Paste original and modified text to compare changes side by side. Monaco diff highlighting makes additions and removals easy to spot.
When do you need to compare two texts side by side?
What this tool does
This diff checker compares an original text against a modified version in a side-by-side Monaco diff editor. Additions appear highlighted on one side, deletions on the other, and both panes scroll in sync so you can review long files without losing your place. Upload files directly or paste content — no account required.
Why you need it
Small edits hide in large documents. A contract revision, config file tweak, or API response change might alter a single line among hundreds. Manual comparison is slow and error-prone; a visual diff surfaces exactly what changed, including whitespace and indentation shifts that are easy to miss by eye.
Developers use diff tools before merging pull requests, after running automated refactors, or when reconciling environment-specific configs. Non-technical teams compare policy drafts, marketing copy, and legal redlines. Because comparison runs locally, confidential drafts and proprietary source code never upload to a server.
How to use it
- Paste the original text into the left pane and the modified version into the right, or use Upload original and Upload modified to load files.
- Review inline highlighting — green-style additions and red-style removals stand out immediately.
- Scroll through both panes together to inspect long documents or multi-file pastes.
- Click Swap sides to flip perspectives, or Clear to start a fresh comparison.
Practical examples
- Config review: Compare staging and production
.envexports to spot the one variable that differs before a deploy. - Code review prep: Paste a function before and after a refactor to verify only intended lines changed.
- Content editing: Diff two versions of a README or policy document to confirm every requested edit landed.
- API debugging: Compare JSON responses from two API versions to identify new or removed fields without a dedicated API diff tool.
How it works
The editor uses Monaco’s built-in diff view, the same engine that powers Visual Studio Code. It computes an edit script between the two inputs and renders changes at intelligent granularity — often word-level for small edits and line-level for larger blocks. Whitespace-sensitive comparison means a tab swapped for spaces shows as a change, which is intentional for code and config work where indentation matters.
Supported upload formats include plain text, JSON, Markdown, JavaScript, TypeScript, CSS, HTML, XML, and YAML. The tool is read-only: it highlights differences but does not merge or resolve conflicts — use Git or your IDE for three-way merge workflows. All text stays in your browser session and is not stored on Kitnax servers.
Common mistakes
- Comparing formatted vs minified: A beautified JSON file diffed against its minified twin will show hundreds of whitespace changes. Format both sides first with the JSON or SQL Formatter.
- Ignoring line-ending differences: Windows CRLF versus Unix LF appears as a change on every line. Normalize line endings before comparing if only content matters.
- Expecting a merge tool: This view is for inspection only. Copy changes manually or resolve conflicts in version control.
- Pasting in the wrong order: Original should be on the left and modified on the right for intuitive addition/removal coloring. Use Swap sides if you pasted backwards.
FAQ
Does it diff line by line or character by character?
Monaco diff uses intelligent granularity — often word or line level depending on change size.
Can I compare files directly?
Yes. Use Upload original and Upload modified to load .txt, .json, .md, .js, .ts, .css, .html, .xml, or .yml files, or paste contents into each pane.
Is there a merge tool?
This is a read-only comparison view. Resolve conflicts in Git or your IDE.
Will formatting-only changes show?
Yes. Whitespace and indentation differences appear as changes.
Is compared text stored?
No. Text exists only in your browser session.