Free Online Text Diff
Compare two pieces of text side by side. See additions, deletions, and changes highlighted line by line - directly in your browser.
What It Does
The capabilities you'd expect from a dedicated text diff tool — nothing less.
- Compare any two blocks of text and see additions, deletions, and unchanged lines highlighted in seconds.
- Switch between inline and side-by-side views to match the kind of diff you want to read.
- Drop or upload files in 60+ formats - code, config, markup, plain text - up to 1 MB each.
- Ignore whitespace-only differences with a single toggle when you only care about real changes.
- Counts of additions, deletions, and unchanged lines are shown beneath every diff.
Common Use Cases
Specific scenarios where this tool earns its place.
Reviewing a Colleague's Edits
Paste the original draft on the left, the edited version on the right, and read every change in one pass instead of skimming a long doc twice. Useful for contracts, specs, and copy reviews.
Spotting Changes Between Two Config Files
Drag a working .env, package.json, or YAML file into one side and a broken one into the other. The diff tells you which line drifted in seconds - faster than tracing through git history.
Comparing Two Versions of an API Response
A backend changed and now your client breaks. Diff the JSON you saved last week against the one you just received and the offending field jumps out, highlighted, in the right column.
Auditing a Refactor Before Committing
Before you push a long branch, paste the old function on one side and the new one on the other. The diff catches the renamed variable, the dropped early return, the off-by-one indent.
Catching Tiny Typos in Long-Form Writing
Paste an old draft of a blog post or release note next to the new one. Word-level diffs show every comma you moved and every sentence you tightened, so nothing slips through copy review.
The Bigger Story
Most people land on a "text diff online" page because they hit a one-off task. We get it - this page exists for that, and the diff above is the real tool. But if you keep finding yourself searching for "json formatter," "regex tester," "base64 encoder," and "diff tool" tab after tab, Start Page HQ is the new tab dashboard that puts all of those - including this Text Diff - on the same page, every single time you open a new tab. Stop bouncing between single-purpose websites and bookmark folders that never sync.
$25/year or $49 lifetime. Free public demo, no signup.
Other Tools You Might Use
Tools developers and writers reach for next, all part of the same dashboard.
JSON Formatter
Format, validate, and minify JSON with line-number errors. Paste an ugly API response and get readable output instantly.
Regex Tester
Live regex matching against sample text with capture groups highlighted. Great pair with diffs when fixing parsers.
Markdown Editor
Draft PR descriptions, issues, or release notes with live preview. Diff the old version against the new before posting.
Base64 & URL Encoder
Encode or decode base64 and URL-safe strings. The other tool you reach for ten times a week building APIs.
QR Code
Generate a QR code for a URL, staging build, or deeplink. Point your phone at it and skip the third-party generator.
Unit Converter
Bytes, milliseconds, hex/decimal, length, weight - the conversions that come up while you debug, without a Google trip.
Notes
Rich-text notes pinned to your dashboard. Stash the snippets you keep diffing so you don't lose them on a tab close.
Quick Note
A scratchpad for the in-between text you paste, edit, and copy. The before-state for almost every diff.
Frequently Asked Questions
Yes. The Text Diff tool above runs entirely in your browser at no cost. The full Start Page HQ dashboard - 50+ widgets, sync across devices, multiple pages - is $25/year or $49 lifetime, and there is a free public demo at startpagehq.com/demo with everything unlocked.
No. The diff runs entirely client-side in your browser. Nothing you paste or upload leaves your device, and we never store, log, or process your text on a server. Safe to use for sensitive code, configs, or contracts.
Yes, once the page is loaded. The diff library and UI are static, so you can disconnect and keep comparing texts. Useful on flaky hotel wifi or behind a strict corporate firewall.
You can upload files up to 1 MB each, in 60+ formats including .js, .ts, .json, .yaml, .md, .py, .go, .css, .html, and plain .txt. For pasted text there is no hard limit, though very large blocks (tens of thousands of lines) will slow down the visual diff.
For a one-off compare it covers the same ground - inline and side-by-side modes, line-level highlighting, ignore-whitespace, file uploads. The difference is that the tool above is one widget on a dashboard with 50+ others (JSON formatter, regex tester, base64 encoder, QR generator), all on the same new tab page. Stop maintaining a bookmarks folder of single-purpose tool sites.