Diff Checker
Compare two texts or code blocks side by side. 100% client-side processing.
No data sent to serverRelated Tools
What is a Diff Checker?
A diff checker compares two pieces of text and shows where they differ — additions, deletions, and modifications. The original Unix diff was published by Douglas McIlroy in 1974 (Bell Labs), and the underlying algorithm has been studied for half a century. Modern implementations like Git's diff and most online tools use variations of Eugene Myers's 1986 algorithm ("An O(ND) Difference Algorithm and Its Variations").
How modern diffs work
The problem is finding the longest common subsequence (LCS) between two sequences. Once you know the LCS, everything outside it is either an addition (in B but not in the LCS) or a deletion (in A but not in the LCS). Myers's algorithm runs in O((N+M)D) where D is the number of edits — fast for similar files, slower for completely different ones.
Granularity: line, word, or character
Diff tools work at different granularities. Line-level is the default for source code — easy to read, matches Git's behavior. Word-level helps for prose where edits are within sentences. Character-level is precise but produces noisy output for typical changes. This tool shows line-level diffs with intra-line word highlighting where helpful.
⚠️ Reference Only
Output is generated based on your input and is provided for reference. Results may vary depending on your specific use case, edge cases, or environment-specific behavior. We do not guarantee accuracy of conversions, validations, or computed values.
Always verify critical outputs against official documentation or production environments. We are not responsible for any decisions or losses based on these tool results.
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