Text Diff Checker
Compare two blocks of text side by side with line-level and character-level diff. Useful for comparing drafts, meta tag changes, schema versions, redirect rules before/after.
Developer Utility
Content review often means diffing the before and after. Do it here, not by eye.
Compare the current version of a page's meta tags to the proposed update. Compare today's robots.txt to the version from before a deploy. Compare two drafts of the same article. Line-by-line diff with character-level highlights makes every change visible.
Inputs
Original (A)
Modified (B)
Diff
Added
0
lines
Removed
0
lines
Modified
0
lines
Unchanged
0
lines
A. Original
B. Modified
Frequently asked questions
What algorithm does the diff use?
Longest Common Subsequence (LCS) at line level, with word-level highlighting inside changed lines.
How large a document can it diff?
Up to ~500k characters per side. LCS is O(nm) so larger inputs slow down.
Can it diff JSON?
Yes, as text. Pretty-print both sides first for cleaner results. For structural JSON diff, use a dedicated tool.
Does it support side-by-side view?
Yes. Default view. Also unified diff view in a separate tab.
Does it respect whitespace?
By default yes. Toggle "ignore whitespace" to compare content only.
What about case-insensitive diff?
Toggle available. Useful when comparing content across case-insensitive systems.
Can I diff two versions of a markdown file?
Yes. Paste both. For HTML or code, same workflow.
Does the diff export?
Copy as unified diff format (standard patch format). Works with
patch command-line.What is a unified diff?
The standard text format for diffs with +/- markers and surrounding context lines. The format
git diff produces.Can I diff large log files?
Up to the size limit, yes. For gigabyte logs, use
diff or git diff on disk.Does it detect moved blocks?
No. LCS treats a moved block as a deletion + insertion. Dedicated move-detection diff tools (like
git diff --color-moved) handle this.Free · no account
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