Paste two versions of any document and see word-level differences highlighted instantly. Added words in green, removed in red — no sign-up, no data sent to any server.
Paste text into both panels, then click Compare
A text compare tool takes two pieces of text as input and produces a diff — a visual representation of the differences between them. Words added in the revised version appear in green. Words removed from the original appear in red with a strikethrough. Words that stayed the same appear in the background, unchanged. The result is an immediate, scannable answer to the question: what is different here?
The SmartWriteTools text compare tool runs entirely in your browser. Paste your original text into panel A, paste your revised version into panel B, and click Compare. The diff appears instantly with a summary showing how many words were added, removed, and left unchanged. No sign-up is required and your text never leaves your device.
When a draft comes back from an editor, a text compare tool shows you exactly what changed. Instead of reading both versions in full and trying to spot differences manually — a slow and error-prone process — you can see all changes highlighted in seconds. This is especially useful for long documents where individual changes are easy to miss.
Contracts often go through multiple revisions. A text compare tool lets you check that only the agreed changes were made between versions. Clause insertions appear in green. Removed text appears in red. Nothing slips through unnoticed.
Students revising essays can use a text compare tool to check that their edits improved the text — and that they did not accidentally delete something important. Tutors can use it to compare submitted work against a previous draft.
When updating website copy, a text compare tool confirms that the new version includes all the required changes and nothing else. This is useful for sign-off workflows where a stakeholder needs to approve the exact changes before publishing.
Software developers use Git for version control. For writers, journalists, and business professionals, a text compare tool provides the same core capability — seeing exactly what changed between two versions — without needing any technical knowledge.
Most text compare tools — including the SmartWriteTools version — use an algorithm called LCS, or Longest Common Subsequence. The LCS algorithm finds the largest sequence of words that appears in both texts in the same order. Words outside that common sequence are marked as additions or deletions.
The quick brown fox jumps
The fast brown fox leaps over
The LCS here is "The brown fox" — three words present in both texts in the same order. "quick" and "jumps" are marked as removed. "fast", "leaps", and "over" are marked as added.
Word-level comparison is more useful than line-level comparison for natural language documents. A file diff tool like Git shows you which lines changed, which is useful for code. A text compare tool shows you which words changed, which is useful for writing — because in a paragraph, a single changed word in the middle of a long line is easy to miss in a line-level diff but immediately obvious in a word-level diff.
File diff tools (Git, diff, WinMerge) compare files line by line. They are designed for source code, configuration files, and structured data where lines are the meaningful unit.
A text compare tool compares documents word by word. It is designed for natural language — prose, essays, articles, contracts, and any document where the meaningful unit is a word rather than a line of code. When comparing two paragraphs of writing, a word-level text compare tool gives a much more readable and useful result than a line-level file diff.
In default mode, Unicode whitespace variants (non-breaking spaces, em spaces, zero-width characters) are normalised to regular spaces — so they do not create false diffs. Enable Strict mode when you need to detect invisible characters, for example when debugging pasted content from a PDF or Word document.
What is the difference between a text compare tool and a diff tool? A text compare tool compares documents word by word, which is useful for natural language content — prose, articles, contracts, and essays. A diff tool (like Git or WinMerge) compares content line by line, which is designed for source code and structured data. For writing, word-level comparison is more useful because a single changed word in the middle of a long paragraph is easy to miss in a line-level diff but immediately visible in a word-level diff.
How does word-level comparison work? The tool uses the Longest Common Subsequence (LCS) algorithm. It finds the longest sequence of words that appears in both texts in the same order. Words outside that common sequence are marked as additions (green) or deletions (red). For example, if Panel A has "The quick brown fox jumps" and Panel B has "The fast brown fox leaps over", the LCS is "The brown fox" — three words present in both texts. "quick" and "jumps" are marked as removed; "fast", "leaps", and "over" are marked as added.
Does the tool check for plagiarism? No. The text compare tool shows differences between two texts you provide — it does not search the internet or reference any external sources. It is a diff tool, not a plagiarism checker. If you need to check whether text was copied from another source, you would need a dedicated plagiarism detection service.
Can I compare very long documents? The tool accepts up to 50,000 characters per panel, which covers most articles, essays, and business documents. For longer texts, compare one section at a time. The LCS algorithm optimises performance for texts up to 500 words in either panel; beyond that, it switches to a simpler comparison mode that maintains accuracy while avoiding browser memory issues.
For a detailed walkthrough with more examples, see our guide Text Compare Tool Online.