Text Diff

Compare two blocks of text and highlight added, removed, and unchanged lines — live, in your browser.

Original Text
Modified Text

Frequently Asked Questions

This tool uses a line-level Longest Common Subsequence (LCS) algorithm — the same basis as the Unix diff command. It finds the largest set of unchanged lines and marks the rest as added or removed.
Lines highlighted in green (prefixed with +) are present in the modified text but not in the original. Lines in red (prefixed with −) were in the original but removed. Unchanged lines are shown without color.
This is a line-level diff. Each line is treated as an atomic unit — if a single character changes, the entire line is shown as removed and re-added. This is the standard behaviour of git diff and the Unix diff utility.
A character-level diff shows the exact characters that changed within a line. A word-level diff compares whole words. A line-level diff (what this tool uses) treats each line as a unit — ideal for code and structured data. Tools like git diff --word-diff offer word-level highlighting on top of a line-level base.
The LCS algorithm finds the largest set of lines that appear in the same order in both texts. Lines in the LCS are marked as unchanged; everything else is marked as added or removed. It uses dynamic programming with an m×n matrix, giving O(mn) time complexity. Very large texts may be slower to process.
This tool is useful when you want to compare a snippet or config file without running git diff. Paste the old version on the left and the new version on the right to see added lines in green and removed lines in red — the same convention used by GitHub, GitLab, and Bitbucket pull request views.
Unified diff format (used by git diff and diff -u) shows changes in a single output block: lines prefixed with - are removals, lines with + are additions. Hunk headers like @@ -1,5 +1,6 @@ indicate line number ranges. This tool uses a similar inline format with color coding.
By default, a line with only whitespace changes is shown as a full removal and addition. Enable Ignore leading/trailing whitespace to suppress these cosmetic differences — useful when comparing code that has been reformatted or pasted from a source that adds indentation.
This tool is a read-only diff viewer — it does not support interactive merging. For full merge capabilities, use git merge, a three-way merge tool like Meld or KDiff3, or the diff/merge feature built into VS Code or IntelliJ.
Lines prefixed with + (shown in green) are present in the modified text but not the original — they are additions. Lines prefixed with − (shown in red) were in the original text but are gone — they are removals. Unchanged lines appear without a prefix and without color.

About This Text Diff Tool

This free text diff tool compares two blocks of text line by line and highlights additions, deletions, and unchanged lines — similar to the output of the Unix diff command. Differences are colour-coded for quick review, and all comparison happens in your browser.

When to use this tool

  • Comparing two versions of a config file, script, or document
  • Spotting changes in an API response after a deployment
  • Reviewing document revisions or draft iterations
  • Identifying which lines differ between two data exports

Standards & References

Related Text Tools

Find & Replace Sort Lines Remove Duplicates Word Counter

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