How does the diff checker work?

It compares the two texts line by line using the longest-common-subsequence algorithm — the same family of logic behind git diff. Unchanged lines stay plain, removed lines are struck through in red, added lines are highlighted in green, and a summary counts each type.

Is my text uploaded to compare it?

No. The comparison runs entirely in your browser with JavaScript — contracts, code, or drafts never leave your device, nothing is stored, and the tool keeps working offline once the page has loaded.

What does “ignore whitespace” do?

It trims each line and collapses runs of spaces and tabs before comparing, so re-indented code or reflowed text doesn’t light up as changed. Your original lines are still shown in the result — only the comparison ignores the spacing.

Can I compare code with it?

Yes — line-based diffing is exactly how developers review code changes. Pair it with “ignore whitespace” when comparing differently indented versions. For very large files, the tool automatically falls back to a simpler comparison instead of freezing your tab.

Does it show which characters changed within a line?

No — this tool diffs whole lines, which keeps results fast and easy to read. A line with a single character changed shows as one removal plus one addition. For most proofreading and code-review jobs, line-level is the right granularity.

Can I compare two Word documents or PDFs?

Paste their text content and yes. Copy each version’s text (Ctrl+A, Ctrl+C in the document) into the two boxes. Formatting like bold or fonts isn’t compared — only the text itself.

Why do JSON files show lots of differences that don’t matter?

Because keys can appear in any order, two equivalent JSON documents can differ on every line. First normalize both through our JSON formatter with “sort keys” enabled, then diff — only genuine data changes will remain.

Text Diff Checker

Compare two texts line by line and see additions and deletions highlighted — private, in-browser diff.

Files never leave your device Instant — no upload waitFree, no sign-up

Original text

Changed text

Ignore whitespaceIgnore case

Compare two texts and see every change — privately

“What changed between these two versions?” is a question worth an exact answer, not a squint. This free text diff checker compares two texts line by line and shows additions in green, deletions in red, and a count of changed lines — using the same longest-common-subsequence approach that powers professional version control diffs.

Nothing to install, nothing uploaded

The documents people diff are precisely the ones that shouldn’t travel: contracts before signing, unreleased copy, proprietary code, exam answers. This tool runs entirely in your browser — both texts stay on your device, nothing is logged, and it works offline once the page has loaded.

Options that handle real-world comparisons

Ignore whitespace stops re-indented code and reflowed paragraphs from drowning the real changes; ignore case does the same for capitalization edits. And because the diff shows your original lines (not normalized copies), the result always reads like your actual document.

Good habits for cleaner diffs

Comparing JSON API responses? Run both through the JSON formatterwith sort keys first, so ordering noise disappears. Comparing lists? Deduplicate them with remove duplicate lines before diffing. Comparing prose with case-only edits? Normalize with the case converter.

Free and unlimited

No sign-up, no document limits, no premium tier. Diff as many revisions as you like — it’s your browser doing the work.

Frequently Asked Questions

How does the diff checker work?
It compares the two texts line by line using the longest-common-subsequence algorithm — the same family of logic behind git diff. Unchanged lines stay plain, removed lines are struck through in red, added lines are highlighted in green, and a summary counts each type.
Is my text uploaded to compare it?
No. The comparison runs entirely in your browser with JavaScript — contracts, code, or drafts never leave your device, nothing is stored, and the tool keeps working offline once the page has loaded.
What does “ignore whitespace” do?
It trims each line and collapses runs of spaces and tabs before comparing, so re-indented code or reflowed text doesn’t light up as changed. Your original lines are still shown in the result — only the comparison ignores the spacing.
Can I compare code with it?
Yes — line-based diffing is exactly how developers review code changes. Pair it with “ignore whitespace” when comparing differently indented versions. For very large files, the tool automatically falls back to a simpler comparison instead of freezing your tab.
Does it show which characters changed within a line?
No — this tool diffs whole lines, which keeps results fast and easy to read. A line with a single character changed shows as one removal plus one addition. For most proofreading and code-review jobs, line-level is the right granularity.
Can I compare two Word documents or PDFs?
Paste their text content and yes. Copy each version’s text (Ctrl+A, Ctrl+C in the document) into the two boxes. Formatting like bold or fonts isn’t compared — only the text itself.
Why do JSON files show lots of differences that don’t matter?
Because keys can appear in any order, two equivalent JSON documents can differ on every line. First normalize both through our JSON formatter with “sort keys” enabled, then diff — only genuine data changes will remain.