Text Compare (Diff Checker)

Two versions of a contract clause, a product description a colleague “lightly edited”, an essay before and after a proofreader, two exports of the same configuration file — spotting what changed by reading both side by side is slow and you will miss things.

This diff checker compares two texts and highlights exactly what changed: removed text struck through in red, added text highlighted in green. Compare word by word for prose, line by line for code and lists, or character by character for short strings such as IDs and URLs.

Options let you ignore differences in capitalization and in spacing, so reformatting doesn't drown out real changes. The comparison runs in your browser, which matters when the texts are confidential.

The algorithm is the same family used by version-control tools: it finds the longest common subsequence of tokens and marks everything else as an insertion or deletion. In practice that means moved sentences show up as a deletion in one place and an insertion in another, which is exactly how a careful reviewer would read them.

How It Works

1. Paste both versions — the original on the left, the changed text on the right. The Swap button reverses them.
2. Pick the comparison unit — word, line or character — and whether to ignore case and extra whitespace. The texts are split into tokens accordingly.
3. Compare — a longest-common-subsequence algorithm finds the smallest set of insertions and deletions, and the result is shown as one merged text with changes highlighted, plus a count of additions and deletions.

Compatibility & Support

Supported Input → Output Formats

• Input: any plain text — prose, code, lists, CSV lines, JSON, configuration files
• Output: highlighted inline diff (deletions struck through, insertions highlighted) and a change count
• Modes: word, line, character; ignore case; ignore extra spaces

Unsupported Formats

Formatting in Word or Google Docs (bold, colours, comments) isn't compared — only the text. Paste plain text, or use the document editor's own compare feature for formatting. For comparing two PDF files visually, use Compare PDF.

File Size Limits

Word and character modes compare up to about four million token pairs — roughly two texts of 1,000 words each in word mode — before asking you to switch to line mode or split the text. Line mode handles much longer documents, such as configuration files of several thousand lines.

The limit exists because a precise diff has to compare every token of one text against every token of the other; doing that inside a browser tab for two full books would freeze the page. Splitting a long document by chapter or section keeps each comparison instant and the highlighted result easier to read.

Who Should Use This Tool?

• Students: A student compares an essay draft with the version returned by a tutor to see every suggested change.
• Freelancers & Designers: A copywriter shows a client exactly which words changed between two versions of a landing page.
• Office Professionals: A legal assistant compares two versions of a clause sent by the other party to catch a quietly altered number.
• Developers: A developer compares two configuration dumps line by line to find the setting that differs between staging and production.

Why This Tool Beats the Alternatives

• Confidential text is never uploaded.
• Three comparison modes instead of line-only diffs.
• Ignore-case and ignore-spacing options.
• Readable merged view — no need to line up two columns by eye.
• Free, instant, no sign-up.

Pro Tips

• Use line mode for code and lists, word mode for prose — word mode on code highlights too much.
• Turn on “Ignore extra spaces” when one version was re-formatted or copied from a PDF, where line breaks and double spaces often change.
• For long documents, compare section by section; the result is easier to review and stays fast. Paste headings into both boxes so you always know which part of the document a change belongs to.

Paste both versions above and click Compare texts.