Text Compare / Diff Checker
Two versions of the same document can look identical at a glance while hiding a changed price, a deleted clause or a reworded sentence. Reading them side by side and hoping to spot the differences is slow and unreliable, especially past a few paragraphs. A diff checker does the comparison mechanically: it lines the two texts up line by line, marks what was removed, what was added and what stayed the same, and gives you a summary count. Writers use it to verify edits, lawyers to check contract revisions, and developers to confirm exactly what a change touched.
Quick Answer: Paste the original text on the left and the revised text on the right, then click Compare. Removed lines appear in red, added lines in green, and unchanged lines stay plain, with a summary of the counts.
How to Use the Text Compare / Diff Checker
- Paste the original version of the text into the left box.
- Paste the new version into the right box.
- Click Compare Texts and wait a moment while the lines are matched up.
- Read the result: red lines were removed, green lines were added, and plain lines are identical in both.
- Check the summary counts to see how large the change really is before reading line by line.
Key Features
- Line-by-line comparison using a proper longest-common-subsequence match, not a naive position check.
- Clear colour coding: deletions in red, additions in green, unchanged lines in neutral text.
- Summary statistics showing added, removed and unchanged line counts at a glance.
- Works for any text: articles, contracts, lists, configuration files and plain code.
- Comparison runs locally in your browser, so confidential drafts are never uploaded.
Best Practices and Tips
- Compare whole documents rather than pasted fragments; a fragment compared against a full text reports misleading additions.
- If a moved paragraph shows as a deletion plus an addition, that is the tool being honest: the words are the same but the position changed.
- Normalise both texts first (same line-break cleanup, same spacing) if you only care about wording changes, not formatting noise.
- For very long documents, compare section by section so the highlighted output stays easy to scan.
Common Mistakes to Avoid
- Comparing texts with different line structures, such as one wrapped paragraph against the same paragraph as separate lines, which floods the result with false changes.
- Assuming green always means better: the checker shows what changed, not whether the change is correct.
- Pasting a document with tracked changes or comments still embedded, which pollutes the comparison with markup.
- Ignoring small changes in numbers: a one-character edit to a price or date is a full line change here and deserves a careful look.
Frequently Asked Questions
How does the diff checker match lines?
It computes the longest common subsequence of lines between the two texts: the largest set of lines that appear in the same order in both. Lines outside that set are reported as removed from the first text or added in the second, which handles inserted and deleted blocks correctly.
Can it compare Word documents?
Paste the text out of each document into the two boxes. Formatting such as bold or fonts is not compared, only the words themselves, which is what matters for content revisions. Save the documents as plain text first if copy-paste carries stray formatting.
What is the maximum size it can compare?
The comparison is quadratic in the worst case, so it is happiest with documents of a few thousand lines. Beyond that, split the document into sections and compare them one at a time for instant results.
Does it highlight changed words inside a line?
This checker works at line level: a line with even one word changed appears as a removal plus an addition, shown as a pair. That keeps the output readable for document-length texts instead of drowning it in character-level markup.
Are the texts I compare kept private?
Yes. The matching runs entirely in your browser tab and nothing is sent to a server, so unpublished and confidential documents are safe to compare here.
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