A text diff checker compares two versions of a text and shows you exactly what changed — every added word, deleted line, and edited sentence. Paste the original contract on the left and the revised version on the right, and within a second the differences light up in red and green. No more squinting at two documents wondering what your colleague actually edited.
This free text diff checker works at both line and word level, offers side-by-side and unified views, and reports stats like similarity percentage. Ignore-case and ignore-whitespace options filter out formatting noise. No signup, no file upload — both texts are compared locally in your browser, so confidential documents never leave your device.
Text Diff Checker
Paste two versions of a text — see exactly what changed, line by line.
🔒 100% private — everything runs in your browser, nothing is uploaded.
How to Use the Text Diff Checker
- Paste the original text into the left box and the modified text into the right box.
- Choose a view: side-by-side places both versions next to each other; unified stacks every change into a single column.
- Pick highlight detail: word level pinpoints changed words inside edited lines, while line level marks whole lines.
- Click “Compare Texts.” The text diff checker aligns both versions and highlights additions in green and deletions in red, with a stats bar showing lines added, removed, unchanged, and overall similarity.
- Copy the diff summary to paste the change list into an email, a code review, or a revision log.
Tick “Ignore case” when capitalization churn would drown out real edits, and “Ignore whitespace” when reformatting is not what you are looking for. If the two texts are identical, the tool tells you so plainly instead of rendering an empty diff.
Features That Set This Tool Apart
- True line alignment: an LCS-based algorithm pairs up matching lines, so moved paragraphs do not create a wall of false changes.
- Word-level highlighting: inside each edited line, only the changed words are marked — you see “Monday” become “Tuesday” at a glance.
- Two professional views: side-by-side for careful review, unified for a compact change log. Switch any time without re-pasting.
- Noise filters: ignore-case and ignore-whitespace toggles keep formatting churn from hiding the edits that matter.
- Similarity score: a single percentage answers “how different are these, really?”
- Copyable summary: export the change list as plain text for reports and documentation.
- Private by design: unlike upload-based tools, this text diff checker compares everything locally — your drafts never touch a server.
Text Diff Checker: Line vs. Word Comparison
Every text diff checker works at two zoom levels, and knowing which to use saves real time. Line-level diff treats each line as one unit: if anything on the line changed, the whole line is marked as removed and re-added. It is perfect for spotting which paragraphs, list items, or code lines were touched, and it keeps the output scannable when documents are long.
Word-level diff goes one step deeper. Once a line is flagged as changed, the tool compares the words inside it and highlights only the ones that differ. Change “The total budget is $5,000” to “The total budget is $7,500” and a word-level view marks just the figure — a line-level view would repaint the entire sentence. For contracts, essays, and config files where single-word edits carry the meaning, word level is the view you want.
This tool gives you both: line alignment first, then optional word highlighting inside each changed pair. Start at line level to find where the edits are, then switch to word level to see exactly what changed. Most online diff tools force you to pick one granularity; here the toggle is one click and never requires re-pasting your texts.
How to Read a Diff Like a Developer
Diffs follow a simple visual grammar. In the unified view, lines starting with a minus sign were removed from the original, lines starting with a plus sign were added in the new version, and plain lines are unchanged context. Side-by-side view shows the same information in two columns: red cells on the left are old content, green cells on the right are new content, and blank cells mean a line exists on only one side.
A few reading tricks help. First, changed blocks usually come in pairs — one deletion plus one addition is a single edit, not two separate events. Second, ignore pure whitespace churn unless formatting is the point of your review; the ignore-whitespace toggle does this automatically. Third, the similarity percentage is your triage shortcut: 98% similar means a quick skim is enough, while 60% similar deserves a careful read.
The conventions come from the classic diff command-line tool, documented in the GNU diffutils manual. Learning this one visual language pays off everywhere — code reviews, legal redlines, and translation QA all use the same red-green grammar.
Everyday Uses for a Text Diff Checker
Beyond code, a text diff checker earns its keep in ordinary office work. Writers and editors diff drafts to confirm a client’s “small tweaks” really were small. Translators compare source revisions against their translations to catch untranslated new sentences. Students diff essay drafts to see how much a paragraph actually changed between revisions.
SEO specialists paste a page’s old and new copy to audit exactly what an agency rewrote — handy when rankings shift after a “minor” content update. Support teams diff knowledge-base articles before publishing to spot accidental deletions. And anyone who has ever received a contract “with just a few changes” knows the value of verifying that claim in ten seconds flat.
Because this checker needs no account and stores nothing, it fits workflows where uploading to a third-party site would be a policy violation: legal drafts, unreleased product copy, HR documents, and anything under NDA.
Text Diff Checker: Frequently Asked Questions
How do I compare two text documents?
Paste the original into the left box and the new version into the right box, then click Compare Texts. The text diff checker aligns the two versions line by line and highlights every addition in green and every deletion in red. You can switch between side-by-side and unified views, toggle word-level highlighting, and copy a plain-text summary of all changes for your records.
What is the difference between line diff and word diff?
A line diff marks an entire line as changed when anything on it differs, which is ideal for finding which paragraphs or list items were touched. A word diff goes further and highlights only the specific words that changed inside each edited line. Use line level to locate edits quickly in long documents, then switch to word level to see the precise changes without re-pasting anything.
Do I have to upload my files to compare them?
No. Many online diff tools ask you to upload files to their servers, but this text diff checker runs entirely in your browser with JavaScript. Your texts are never sent anywhere, stored, or logged, so it is safe for confidential contracts, unreleased copy, and personal documents. It even keeps working offline once the page has loaded.
What do the red and green highlights mean?
Red marks content that exists in the original but was removed or replaced; green marks content that is new in the modified version. In the unified view these appear as minus and plus lines. A red-green pair sitting together almost always represents a single edit — one old line replaced by one new line — rather than two independent changes.
Can this tool compare very long documents?
Yes, up to about 3,000 lines per side, which covers most articles, contracts, and configuration files comfortably. Beyond that the comparison can get slow in a browser tab, so the tool will ask you to split the text. For the best results with long documents, use line-level view first to find the changed regions, then zoom into word level.
Related Free Tools
- Add Line Numbers — number every line before diffing, so changed lines are easy to reference.
- Text Reverser — flip text or lines for puzzles, testing, and formatting experiments.
- Case Converter — normalize capitalization across both versions before comparing.
- All Free Tools — browse the complete collection of free writing and productivity tools.
Whether you are reviewing a contract, auditing an SEO rewrite, or checking your own revisions, a fast text diff checker turns “what changed?” from a guessing game into a ten-second answer. Paste both versions above and see every edit highlighted — no signup, no upload, no guesswork.