How do I compare two texts?
Paste the original into the first box, paste the new version into the second, and click Compare. The result shows one merged text: words that appear only in the second version are marked as added, words that appear only in the first are struck through, and unchanged words stay as they are. Above it you get the counts and a similarity percentage.
How the comparison works
The tool splits both texts into words and finds the longest sequence of words they share, in order. Everything outside that shared sequence is reported as added or removed. This is the same idea used by "diff" tools for code, applied to words instead of lines.
| Result | Meaning |
|---|---|
| Added | Words in the second text but not in the first |
| Removed | Words in the first text but not in the second |
| Same | Words present in both, in the same order |
| Similarity | Shared words relative to the size of both texts, as a percentage |
What it is good for, and what it is not
It is good for seeing what changed between two versions of the same text. It is not a plagiarism checker. A high similarity score between two pasted texts only says that they share words in order. It does not search the web or any database, and it does not tell you whether either text is original. To look for matching passages in open sources, use the Plagiarism Checker, and see its page for the sources it searches and its limits.
Limits to keep in mind
- The comparison is word-based. Words are compared as exact tokens, so a changed capital letter or attached punctuation (for example "end" versus "end.") counts as a difference, while extra spaces and line breaks do not. A moved paragraph may appear as one removal and one addition.
- It does not understand meaning. A changed word that reverses the sense, such as "must" to "must not", appears as a small change, so read the highlighted result carefully.
- Very long texts may be slow, because the comparison grows with the size of both texts. For long documents, compare them section by section.
- Formatting such as bold, tables and comments is not compared, only the pasted text.
Tips
Clean up stray line breaks and double spaces first with the Text Cleaner if the texts came from different sources, then compare. For a rewrite you want to check, the Paraphrasing Tool output pairs naturally with this page.