Free Diff Checker — Compare Text Online
Paste two versions of any text or code and instantly see every added and removed line. Runs entirely in your browser — nothing is uploaded, your content stays on your device.
Both texts are compared in your browser — nothing is uploaded.
How to Compare Two Texts in Your Browser
Paste both versions
Drop the original text into the left box and the changed version into the right — plain text, code, JSON, config, a document, anything.
Choose line or word mode
Line mode highlights whole changed lines (best for code and configs); word mode pinpoints the exact words that changed (best for prose).
Read the highlighted diff
Added content is highlighted in one colour and removed content in another, with a running count of additions and deletions — no signup, no upload.
Everything You Need to Compare Text
A diff checker should make changes obvious at a glance and keep your content private. Here's how this one does both.
Line and word diff
Switch between line-level comparison for code and structured files, and word-level comparison that catches a single changed word in a paragraph.
Clear add / remove highlighting
Additions and deletions are colour-coded with +/− markers and a live count, so you see exactly what changed and how much.
Handles code and prose
Compare source files, JSON, config, contracts, essays, or translations — the diff works on any text, with monospaced output that keeps code aligned.
Private — nothing uploaded
Both versions are compared in your browser. Since diffs often involve unreleased code or sensitive documents, nothing is ever sent to a server.
When You Need a Diff Checker
Any time two versions of something need reconciling, a diff makes the change obvious. These are the common cases.
Review code changes
Compare two versions of a function, file, or snippet to see exactly what was added or removed before you commit or paste it back.
Proofread document edits
Spot every change between two drafts of an article, contract, or email — including a single reworded sentence you might otherwise miss.
Compare config or data
Diff two JSON payloads, environment files, or CSV exports to find the one value that changed between environments or runs.
Check translations and copies
Line up two translations or two copies of a text to confirm they match, or to find where they drift apart.
Compare Text Without Uploading It
Many online diff tools send both texts to their server to compute the difference. Since you're often comparing unreleased code or private documents, doing it locally is the safer choice.
In-browser with SupaTools
- Both texts are compared on your device, never uploaded
- Line and word diff modes in one place
- Clear +/− highlighting with a live change count
- Free with no sign-up and no size limit
Typical online diff tools
- Your code and documents sent to their server
- Unclear how long the input is logged or stored
- Often line-only, missing word-level changes
- Ads or sign-up walls on larger inputs
Pro Tips for Comparing Text
Use line mode for code
Source code and config files compare best line-by-line, matching how you read and edit them and how version control shows changes.
Use word mode for prose
For paragraphs, word mode highlights the exact words that changed instead of flagging the whole line, so small edits stand out.
Normalize before comparing
If only formatting differs, run both sides through a formatter first so the diff shows real content changes, not whitespace noise.
Diff Checker — Frequently Asked Questions
Compare Your Text Free — No Sign-Up
Paste two versions above and see every change instantly. Both texts stay in your browser — nothing is uploaded.