Text comparator
Compare two versions of a text side by side. See line-level and character-level diffs, plus a similarity percentage so you know how close the two versions really are.
How the similarity score works
We use Google’s diff-match-patch library, which finds the smallest edit script between two strings and reports the Levenshtein distance. The similarity percentage is 1 - (distance / max(left, right)). So an 80% similarity means about one in five characters changed between the two versions.
This tool is for revising your own writing, comparing two drafts, or spot-checking paraphrased content. It is not a plagiarism detector — for that you need a service with a large reference corpus.
About the Text comparator
The text comparator puts two versions of a text side by side and highlights exactly what changed. It shows a line-by-line view, where altered, added, and removed lines are colour-coded, and an inline character view that marks the precise insertions and deletions within the text. It also reports a similarity percentage and a running count of characters added and removed.
Reach for it when you are revising your own writing, reconciling two drafts, checking what an editor changed, or spot-checking a paraphrase against its source. It answers the question 'what is actually different here, and how different is it' without you reading both versions line by line. Everything is computed in your browser as you type, with a Swap button to flip the two sides.
How to use it
- Paste the first version into the Original box on the left.
- Paste the second version into the Revised box on the right.
- Read the similarity percentage and the green plus and red minus character counts in the summary bar.
- Open the Line by line tab to see whole lines marked as changed, added, or removed in context.
- Open the Inline (character) tab to see the exact characters inserted or deleted, then use Swap to reverse the comparison if needed.
Examples
Checking an editor's changes
Paste your submitted paragraph as Original and the returned version as Revised. The line view flags the two sentences that changed, the inline view shows a deleted clause in red and a new phrase in green, and the summary reads something like 94% similar with +18 and -7 characters.
Reconciling two drafts
Compare draft A and draft B of an intro. The similarity score gives you a quick gut sense of how far apart they are, while the line-by-line panel shows which paragraphs are identical and which diverged, so you can merge the best of each instead of rereading both top to bottom.
Frequently asked questions
- How is the similarity percentage calculated?
- It uses Google's diff-match-patch to find the Levenshtein edit distance between the two texts, then reports 1 minus distance divided by the length of the longer text. So 80% similarity means roughly one character in five differs between the versions.
- Is this a plagiarism checker?
- No. It only compares the two texts you provide. It has no reference corpus and does not search the web, so it cannot tell you whether text was copied from elsewhere. It is built for comparing drafts and revisions you already have.
- What is the difference between the line and inline views?
- The line view compares whole lines and marks each as same, changed, added, or removed, which is best for structural edits. The inline view diffs character by character and highlights the exact insertions and deletions, which is best for small wording tweaks.
- What do the +18 and -7 numbers mean?
- They count characters, not words: how many characters were inserted into the revised version and how many were removed from the original. A pure rewrite shows large numbers on both sides, while a typo fix shows just a few.
- Does the order of the two boxes matter?
- It affects which side is labelled removed versus added, but not the similarity score, which is symmetric. Use Swap to flip the two texts if you want to view the change from the other direction.
Good to know
The comparison is purely textual, so it reacts to every character including whitespace and capitalisation. Two paragraphs that read the same but use different line breaks or trailing spaces will register as changed. If you only care about wording, normalise spacing in both versions first so the diff focuses on real edits.
Similarity is a blunt instrument: a high percentage means few characters changed, not that the meaning is preserved, and a single reordered sentence can lower the score more than its impact warrants. Read the highlighted diff rather than trusting the number alone. For revising your own work the inline character view is usually the most useful, because it points straight at the words you altered, while the line view shines when you have moved or rewritten whole blocks.