What does a diff checker show?

It compares two text versions line by line, highlighting lines that were added (green in Version B), removed (red from Version A), or unchanged (grey in both).

Can I compare source code with this tool?

Yes. It works on any plain text — source code, JSON, HTML, CSS, YAML, Markdown, SQL or prose — comparing line by line regardless of content type.

Is the comparison case-sensitive?

Yes by default. Enable the Ignore case option to treat lines with different capitalisation as identical — useful when comparing text that may have been reformatted.

How many lines can I compare?

The tool handles large documents in your browser. Performance is good up to several thousand lines; very large files (10,000+ lines) may be slow depending on your device.

Is my text uploaded to a server?

No. All comparison runs locally in your browser using JavaScript. Your text never leaves your device — safe for confidential documents, code or legal text.

What is the difference between this and a git diff?

Git diff compares file versions tracked in a git repository. This tool compares any two pieces of text you paste directly — no git repository, no file system, no command line needed.

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Text Diff Checker

Compare two pieces of text side by side and highlight every addition, deletion and change. Free, private, runs in your browser.

📝 Text Tools Free Browser-based

Tool

Original (Version A)

Modified (Version B)

Ignore case Ignore leading/trailing whitespace

What Is a Text Diff Checker?

A text diff checker compares two versions of any text side by side and highlights exactly what changed — which lines were added, removed or stayed the same. This is the same technology used by Git to show code changes, but applied to any plain text: documents, config files, data exports, web copy or legal text. Instead of manually reading two versions and trying to spot differences, a diff checker shows you the changes instantly and precisely.

Reading the Diff Output

Green lines — present only in Version B (added in the new version).
Red lines — present only in Version A (removed from the original).
Grey lines — identical in both versions (unchanged context).

Common Use Cases

Document revision tracking — compare two drafts of an essay, report or proposal to see exactly what changed.
Code and config review — spot differences between two versions of a config file, script or JSON payload.
SEO content audits — compare updated web page copy against the previous version before publishing.
Contract and legal text — identify clause changes between document versions quickly and accurately.
Data validation — verify that two CSV or JSON exports are identical line for line.
Translation review — compare a source text against a translation to check completeness.

Line-by-Line vs Word-by-Word Diff

This tool performs a line-by-line diff, which is the standard approach for code and structured text. For flowing prose where a single sentence edit causes many line changes, try reformatting your text with one sentence per line before comparing — this gives a cleaner, more readable diff output.

How the Diff Algorithm Works

Under the hood, this tool uses the longest common subsequence (LCS) algorithm — the same algorithm powering Git's diff command and most code review tools. LCS finds the largest set of lines that appear in both versions in the same order, then marks everything else as added or removed. This approach minimises the number of reported changes, making the diff as readable as possible. For very large texts (thousands of lines), the algorithm runs in O(n²) time, so results may take a second or two to compute — this is normal and all processing happens in your browser with no server round-trip.