Text Diff Checker
Compare two blocks of text and instantly see every added, removed, and unchanged line — 100% in your browser.
Paste text into both fields above — the diff appears live below.
When you need to know exactly what changed between two pieces of text, a diff tool is the fastest way to find out. Instead of reading both versions word by word, a diff viewer isolates every insertion, deletion, and unchanged passage, saving you time and reducing the chance of missing something subtle.
How to use the Text Diff Checker
Paste your original text into the left panel and your changed version into the right panel. The diff output appears immediately below both fields — no submit button required. Added lines are highlighted in green with a + prefix; removed lines are in red with a - prefix; unchanged lines are shown in a muted colour for context. A summary badge at the top tells you the total number of added and removed lines at a glance.
Common use cases
- Code review: Paste two versions of a function or configuration file and spot regressions or missed changes instantly.
- Document editing: Compare a draft with a revised version to verify that every intended edit was applied and nothing was accidentally deleted.
- Data validation: Check whether two CSV or JSON exports that are supposed to be identical have drifted out of sync.
- Debugging: Compare the expected output of a script with its actual output to find exactly where the two diverge.
- Contract & legal text: Identify every clause that changed between two versions of an agreement before signing.
About the diff algorithm
This tool uses the Myers diff algorithm, the same algorithm that powers git diff and most professional code review tools. It finds the minimal set of changes that transforms the original text into the changed text — meaning it won't invent spurious differences or miss real ones. Long unchanged sections are collapsed automatically to keep the output readable, with a click-through to expand if needed.
Privacy
Everything runs entirely in your browser. Your text is never uploaded to any server, stored in a database, or transmitted over the network. You can safely paste confidential source code, internal documents, or private data without concern. There are no accounts, no logs, and no rate limits.
Try the "Try an example" button at the top right to see a realistic JavaScript refactor diff — it shows how the tool highlights template-literal modernisation, new parameters, and added function calls side by side.
Frequently Asked Questions
How does the Text Diff Checker work?↓
It uses the Myers diff algorithm (via the jsdiff library) to compare your two texts line by line. Added lines appear in green, removed lines in red, and unchanged lines are shown in muted grey for context. The result updates instantly as you type — no button click needed.
Is my text sent to a server?↓
No. All comparison happens entirely inside your browser using JavaScript. Your text never leaves your device, which makes it safe for sensitive content like passwords, source code, or confidential documents.
What is a "diff" and when should I use one?↓
A diff (short for difference) highlights exactly what changed between two versions of a document. Use it when reviewing code changes, proofreading revised drafts, auditing configuration files, or debugging why two outputs that should be identical differ.
Can I compare code with this tool?↓
Yes. The diff viewer uses a monospace font and preserves indentation and whitespace, making it well-suited for comparing source code, JSON, YAML, SQL, and any other structured text format.
What do the +adds / -dels counters mean?↓
The badge at the top shows the total count of added lines (lines present only in the changed text) and removed lines (lines present only in the original text). Unchanged lines are not counted.