Text Diff Checker Online (100% Free & Private)
Free text diff checker that runs in your browser. No sign-up, no install.
Text Diff Checker
Compare two texts line by line, with the exact changed words highlighted inside modified lines.
Lines are matched with a longest-common-subsequence diff, so an inserted or deleted line does not mark everything after it as changed. When a removed line and an added line are similar, they are shown as one modified line with the changed words highlighted. Moved blocks show up as a removal plus an addition. Everything runs in your browser.
What this tool does and who it is for
Paste an original and a changed version and see exactly what differs. Lines are matched with a longest-common-subsequence diff, so an inserted or deleted line does not make everything after it look changed, and inside modified lines the exact words that changed are highlighted.
You get counts of added, removed, modified and unchanged lines, a side-by-side view on larger screens and a stacked view on phones, plus options to ignore whitespace and letter case.
The comparison runs in your browser and your text is not uploaded.
Official Formula / Technical Standard
Real-World Worked Scenario
Enter or paste your text to perform instant transformations, count characters, and analyze typographic properties.
When people use it
Comparing two drafts of a document
Paste the old and new text to see every wording change without hunting for it.
Checking a contract or policy revision
Highlight which sentences were added or removed between versions. For legal documents, still read the full text.
Comparing config files or code snippets
Find the one line that differs between two settings files.
Checking a copy-edit
Ignore whitespace to focus on real wording changes after reformatting.
Notes for US users
- Contracts, leases and employment documents often change in small wording details. A diff helps you notice them, but it is not legal advice.
- Paste from Word or PDF can add odd spacing. Turn on Ignore whitespace if lines look different but read the same.
- Line endings (Windows vs Mac or Linux) are normalized, so they do not show up as differences.
Limits and what to double-check
- •It compares plain text only. Formatting such as bold, comments and tracked changes in Word is not part of the comparison.
- •A paragraph that was moved shows as a removal in one place and an addition in another rather than as a move.
- •Very large inputs, where the two texts have millions of line pairs to compare, are refused to keep your browser responsive. Compare them in sections.
Expert Best Practices & Common Pitfalls
Recommended Best Practices
- •Review formatted text for readability and natural sentence flow.
- •Match casing and formatting conventions to your target platform or style guide.
- •Keep working drafts saved in your primary document editor.
Common Mistakes to Avoid
- •Relying entirely on automated tools without conducting human proofreading.
- •Using aggressive formatting or excessive capitalization in professional communications.
- •Pasting sensitive confidential drafts into untrusted web tools.
Features & Security Architecture
- 100% Client-Side: Zero server uploads ensure complete privacy and data confidentiality
- Fast Results: Processing happens on your own device, so there is no upload or server queue to wait for
- No Sign-Up Required: Completely free to use with no daily usage caps or account requirements
- Works on All Devices: Fully responsive across desktop, tablet, and mobile browsers
Frequently Asked Questions
How does the Text Diff Checker work?▼
The Text Diff Checker runs 100% inside your web browser using modern client-side JavaScript. It performs calculations, conversions, and document processing locally on your device without sending any data to external servers.
Is this text diff checker completely free to use?▼
Yes. This tool is completely free with no usage limits, no subscriptions, and no registration required.
Is my data private when using the Text Diff Checker?▼
Yes. Because all operations execute locally on your computer or phone, your inputs, documents, and data never leave your browser.
How is this different from comparing line 1 to line 1?▼
It finds the longest set of lines that appear in both versions in the same order, so one inserted line does not shift everything below it into a false difference. Only lines that truly changed are marked.
What does a modified line mean?▼
When a removed line and an added line are similar enough, they are shown as one changed line and the exact words that differ are highlighted. Unrelated lines show as a plain removal and a plain addition.
What do the ignore options do?▼
Ignore whitespace treats runs of spaces and tabs as equal and ignores leading and trailing spaces. Ignore case treats uppercase and lowercase letters as the same. Both apply to line and word comparison.
Can I compare two files?▼
Open each file in a text editor, copy the contents and paste them into the boxes. The tool compares pasted text, not uploaded files.
Is my text private?▼
Yes. It is compared in your browser and nothing is sent to a server.