Does this compare word-by-word or character-by-character?

No — this is a line-based diff, comparing whole lines against each other. A single-character change within a line will show that entire line as removed and re-added, not just the specific character that changed.

Will differences in whitespace show up?

Yes — lines are compared as exact text, so a line with different leading or trailing whitespace registers as a change even if it looks visually identical to the other version.

Is there a size limit?

Very large inputs can take a noticeably long time, since this diff approach scales with the product of both texts' line counts. For a typical code file or config comparison this is fast; for genuinely huge files, a dedicated command-line diff tool will perform better.

What happens if a line just moved to a different position?

If the line's text is otherwise identical and it still appears in both versions, it's correctly recognized as unchanged rather than being reported as a remove-and-add pair — that's the specific advantage of an LCS-based diff over a naive position-by-position comparison.

Code Diff Checker

Compare two blocks of code or text line by line, with additions and removals clearly marked.

TL;DR: Code Diff Checker is a free, browser-based tool that lets you compare two blocks of code or text line by line, with additions and removals clearly marked.

Original

Changed

About this tool

Compare two blocks of code or text line by line, highlighting exactly what was added, removed, or left unchanged between them. Uses the same longest-common-subsequence approach behind most real diff tools, so lines that only moved or repeat elsewhere aren't misleadingly flagged as changed — the comparison finds the smallest actual set of differences between the two versions, not just a naive line-by-line mismatch.

Key Features

Line-by-line comparison using a proper longest-common-subsequence diff
Clearly marks added, removed, and unchanged lines
Works on any plain text, not just code — configs, prose, data files
Runs entirely in your browser — neither side of the comparison is ever uploaded
Handles reordered or repeated lines correctly, not just naive position matching

How to Use

Paste the original version on the left.
Paste the changed version on the right.
Click Compare to see the line-by-line diff.

When to use it

Reviewing what actually changed between two versions of a config file or script
Comparing a draft against a previous revision before committing changes
Spotting exactly what's different between two versions of a document or data export
Checking whether a code snippet you were given differs from your own working version
Verifying a find-and-replace or refactor didn't change more than intended

Tips & limitations

This is a line-based diff — it compares whole lines against each other, not individual characters or words within a line, so a single-character change still shows the entire line as removed-and-re-added
Lines are compared as exact text — differences in leading whitespace or trailing spaces will register as a change even if the visible content looks the same
Very large inputs (several thousand lines on either side) can take a noticeably long time to compare, since this style of diff algorithm scales with the product of both lengths — for genuinely huge files, a dedicated command-line diff tool will be faster
A line that moved to a different position but is otherwise identical is correctly recognized as unchanged, not as a remove-and-add pair, as long as it still appears somewhere in both versions

How the comparison actually works

Example: one line changed, one line added
Original	Changed	Result
line two	line TWO	Shown as removed + added (different text)
(not present)	line five	Shown as added only
line three	line three	Shown as unchanged

This is built on the longest common subsequence algorithm — the same underlying approach tools like diff and Git use — which finds the longest sequence of lines common to both versions, then reports everything else as either removed from the original or added in the changed version.

Frequently Asked Questions

: No — this is a line-based diff, comparing whole lines against each other. A single-character change within a line will show that entire line as removed and re-added, not just the specific character that changed.
: Yes — lines are compared as exact text, so a line with different leading or trailing whitespace registers as a change even if it looks visually identical to the other version.
: Very large inputs can take a noticeably long time, since this diff approach scales with the product of both texts' line counts. For a typical code file or config comparison this is fast; for genuinely huge files, a dedicated command-line diff tool will perform better.
: If the line's text is otherwise identical and it still appears in both versions, it's correctly recognized as unchanged rather than being reported as a remove-and-add pair — that's the specific advantage of an LCS-based diff over a naive position-by-position comparison.

Cite This Tool

Referencing this tool in a paper, article, or bibliography? Copy a ready-made citation below.

NexLove.org. (2026). Code Diff Checker [Software]. https://nexlove.org/tools/code-diff-checker.html

“Code Diff Checker.” NexLove.org, 2026, nexlove.org/tools/code-diff-checker.html.

NexLove.org (2026) Code Diff Checker. Available at: https://nexlove.org/tools/code-diff-checker.html (Accessed: 2026).

@misc{nexlove_code_diff_checker,
  title = {Code Diff Checker},
  author = {{NexLove.org}},
  year = {2026},
  url = {https://nexlove.org/tools/code-diff-checker.html}
}

Embed This Tool

Add the live Code Diff Checker tool to your own website with this snippet — it loads the real, working tool in an iframe, not a static screenshot.

<iframe src="https://nexlove.org/embed/code-diff-checker.html" width="100%" height="600" style="border:1px solid #e2e8f0;border-radius:12px" title="Code Diff Checker — NexLove.org" loading="lazy"></iframe>

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