How to use
- Paste the original version into the left box and the changed version into the right box.
- Choose whether to compare by lines or by words. Lines suit lists, code and data; words suit sentences and paragraphs.
- Read the summary of added, removed and changed items, then scan the highlighted result.
- Use Swap sides if you pasted the versions the wrong way round.
When to compare two texts
Documents change hands many times. A contract comes back from the other side, a colleague edits your report, an essay goes through several drafts, or a configuration file behaves differently on two servers. Reading both versions side by side to spot the difference is slow and unreliable. This tool matches the two versions and shows exactly what was added, removed or changed.
Lines or words?
Line mode compares the texts one line at a time. It is the right choice for lists, code, CSV data and any text where each line is a separate item. A line that differs by even one character is shown as removed from the original and added in the new version.
Word mode compares the words inside the text and ignores differences in spacing. It works best for prose, where sentences wrap freely and a single edit can shift line breaks. Changed words are highlighted in place so you can read the new version with the edits marked.
How the matching works
The tool finds the longest sequence of lines or words that the two versions share, keeps those as unchanged, and marks everything else as added or removed. This is the same approach used by version control systems such as Git. When a removed block is directly followed by an added block, the summary counts it as a change, pairing the lines or words one by one.
Example
Original: “The meeting starts at 9 and ends at 11.” New: “The meeting starts at 10 and ends at noon.” In word mode the result marks “9” and “11.” as removed and “10” and “noon.” as added. The summary shows 2 changed words and nothing added or removed on its own.
Tips
If the result shows many changes you did not expect, the texts may differ in invisible characters or line endings. Run both through the whitespace cleaner and compare again. When comparing long documents, switch to line mode first to find the changed paragraphs, then paste just those paragraphs and use word mode for the details.
Frequently asked questions
- How are additions and removals shown?
- Added text is underlined with a green background and removed text is struck through with a red background. In line mode each line also starts with a plus or minus sign, so the result can be read without relying on color.
- What counts as a change?
- When something is removed and something else is added in the same place, the pair is counted as a change instead of one removal plus one addition. If three lines replace two, that is two changes and one addition.
- Does the comparison ignore extra spaces?
- In word mode, differences in the amount or type of whitespace are ignored, so a double space or a line break where there used to be a space does not count as a change. In line mode every character of a line matters.
- Why does a punctuation change mark the whole word?
- Word mode compares whole words separated by spaces. "end." and "end" are different words, so the full word is shown as changed. This keeps the result readable, especially for Korean where a single word can carry several grammatical endings.
- Is there a size limit?
- No fixed limit. Comparing two documents of a few thousand lines works well in a modern browser. Very large texts take longer because every line has to be matched.
- Are my texts uploaded?
- No. The comparison runs in your browser and both texts stay on your device. They are saved in this browser's local storage so they are still there when you come back.