Text Diff Checker
Compare two blocks of text line by line and see exactly what was added, removed, or unchanged — free, private, and works entirely in your browser.
Your result
Updates as you type- Similarity
- 100%
- Original lines
- 0
- Changed lines
- 0
Compared lines match with the selected options.
More result details
Diff
Nothing to compare yet.
Method, assumptions, and tips
Optional comparison normalizes extra whitespace and case while preserving original text for display. Word highlighting refines changed line pairs; similarity remains a line-based percentage.
Line counts and similarity compare whole lines. Changed line pairs also highlight individual word edits; a one-word edit still counts as a removed line and an added line.
Comparison is exact by default. Advanced options can trim and collapse whitespace within each line or ignore case; original text remains visible in the result.
Similarity percentage is unchanged lines divided by the longer side's total line count.
The diff uses a longest-common-subsequence comparison of lines. Other diff tools can choose different alignments when lines repeat.
The comparison runs entirely in your browser as you type — neither text is ever uploaded to a server.
Paste the older version as "Original" and the newer one as "Changed" — the +/- signs in the diff only make sense in that direction.
Spotting exactly what changed between two drafts of a document, two versions of a config file, or two paragraphs of copy.
How it works
Compare drafts while keeping the original wording visible
Paste or import the before and after versions. The summary counts added, removed and unchanged lines. A changed line is normally a removal followed by an addition, so a one-word edit can increment both counts. Word highlighting within changed line pairs helps locate the edit without changing those line counts.
Example: a small edit with a large meaning
Compare these two lines:
The service is available.The service is not available.Expect one removed line, one added line and zero unchanged lines. The similarity score is 0% because neither line matches. The added word reverses the meaning; the score itself does not assess that meaning. Conversely, one changed line in a long document can leave a high similarity score even if it changes an important price or permission.
Choose what differences count
By default, leading spaces, trailing spaces and capitalization count as differences. In the comparison controls, Ignore whitespace differences trims each line and collapses runs of whitespace inside it to a single space. It does not remove line breaks or make a single-word spelling out of separated words. Ignore capitalization compares lowercase forms. Both settings affect the comparison while keeping original text visible.
For example, Hello world and hello world differ with default settings. Enable both options and the lines compare equal. A 100% similarity score with options enabled means the normalized lines match, not that the original files contain identical bytes. Leave whitespace comparison exact when indentation or spaces are meaningful to the file format.
Read the summary and the detailed view together
| Measure | What it means |
|---|---|
| Added lines | Lines present only in the second sequence |
| Removed lines | Lines present only in the first sequence |
| Unchanged lines | Matching lines retained by the comparison, after any chosen normalization |
| Similarity | Unchanged lines divided by the longer document’s line count |
Use the changes-only view to reduce noise, navigate between changes, or switch to a unified display. The downloaded comparison is a readable diff; check the original files before applying changes elsewhere. Reordered lines can appear as a removal and an addition rather than a move. Repeated lines can admit more than one valid alignment.
Text comparison or JSON comparison?
Use this page to review wording, whitespace or source text. Use JSON Diff Checker for JSON data when formatting and object-key order should not count. A text diff does not parse a configuration language or establish that an edit is valid.
Each input supports up to 2,000 lines. The local file importer accepts up to 200 KB. Larger documents should be split into relevant sections; line-based comparison allocates work according to both inputs’ sizes. Processing stays in your browser, and Share copies the tool URL without including either text.
FAQ
Can I highlight changed words or ignore whitespace and capitalization?
Yes. Changed line pairs highlight edited words. The input controls can normalize extra whitespace and case while preserving the original text for display. Changes only hides unchanged lines; Unified view and previous/next navigation focus the edits. Similarity remains a line-based comparison, not a measure of meaning.
Why does a single changed word show as a whole line removed and added?
The comparison works line by line, not word by word. If any part of a line differs, the whole line counts as changed — shown as the old version removed and the new version added, usually right next to each other in the output. Reading the two adjacent lines together shows exactly which word changed.
Is the comparison case-sensitive?
Yes by default. Enable Ignore capitalization in the comparison controls for case-insensitive comparison. Original text stays visible, so matching normalized lines can still look different.
Does it ignore extra whitespace?
Comparison is exact by default. Enable Ignore whitespace differences in the comparison controls to trim each line and collapse internal whitespace runs to one space. Line breaks still matter, and original text remains visible.
What does the similarity percentage actually measure?
The number of unchanged lines divided by whichever input has more lines, as a percentage. It is a rough size-of-change indicator, not a measure of how much the meaning changed — a tiny edit that flips a critical word can still show a very high similarity score, so always check the actual diff too.
Can I compare two files, not just pasted text?
Yes. Use Import local file above each input for plain text files up to 200 KB, or paste their contents. Files are read locally without uploading.
Which text should go in "Original" versus "Changed"?
Put the earlier version in "Original" and the newer one in "Changed." The +/- markers are directional: a line prefixed with - was in the original and removed; a line prefixed with + is new in the changed version. Swapping the two boxes reverses every +/- marker.
Why do reordered lines show as removed and re-added instead of "moved"?
The underlying algorithm finds the longest sequence of lines common to both texts in their original order — it does not have a concept of a line "moving." If you reorder two lines, the comparison will typically show one as removed from its old position and added at its new one, since that is the smallest true difference between the two orderings.
Is there a limit to how much text I can compare?
Up to 2,000 lines per side; local file imports also have a 200 KB limit. Comparison work grows with the product of the two line counts, so large inputs can take longer depending on your device. Split longer documents into relevant sections.
Is my text uploaded anywhere?
No. This tool processes both texts locally in browser memory and does not send their contents to a server or save them in persistent storage. Share copies only the tool URL. Follow your organization’s rules for handling confidential material.
Can this compare code files?
Yes — the line-by-line method is exactly how tools like `git diff` compare source code. Paste two versions of a file to see precisely which lines changed, were added, or were removed.