Is my text uploaded to a server?

No. The comparison runs only in your browser with a plain longest-common-subsequence (LCS) algorithm. Nothing is sent, logged, or stored - so configs, logs, and contracts stay on your device.

How is this different from Diffchecker or Text-Compare?

Many popular online diff sites upload your text to their servers (even over HTTPS). This page never uploads. You also get free ignore-whitespace, ignore-case, hide-unchanged, word-level highlights, and a copyable unified diff without an account.

What does Ignore whitespace do?

It normalizes runs of spaces and tabs and trims each line before comparing. Useful when one side was reformatted or when Windows vs Mac line pastes changed indentation.

What is a changed line versus added or removed?

When a removed line sits next to an added line, the tool pairs them as a change and runs a second word-level LCS so you see which tokens moved. Pure inserts and deletes stay as added or removed.

How is similarity calculated?

Similarity is based on how many lines the LCS shares relative to both sides: (2 × shared lines) ÷ (left lines + right lines), shown as a percentage. Identical texts score 100%.

Is there a size limit?

Yes. Each side is capped at 4,000 lines so the browser LCS table stays responsive. For larger files, compare a section at a time or split the file.

Text Tools

Diff Checker

Paste an original and a changed version to see added, removed, and modified lines.

Nothing is uploaded. Compare configs, logs, and contracts in your browser - Diffchecker and server-side tools cannot claim that.

Ignore whitespaceIgnore caseHide unchanged lines

Original

Changed

About Diff Checker

Paste an original and a changed version to see added, removed, and modified lines. This free Diff Checker runs a longest-common-subsequence compare entirely in your browser - nothing is uploaded - so it is safe for config files, logs, and contracts. That is the one claim Diffchecker and other server-side tools cannot make. Toggle ignore whitespace or ignore case, hide unchanged lines, and copy a unified diff summary.

How to Use Diff Checker

Paste the original text on the left and the changed text on the right. The diff updates as you type.
Optionally turn on Ignore whitespace or Ignore case to skip formatting noise.
Review the side-by-side view: removals in red, additions in green, and word-level highlights inside changed lines.
Use Hide unchanged lines to collapse long files down to the edits only.
Copy the diff summary (counts + unified patch) when you need to paste the result elsewhere. Nothing leaves your browser.

Diff Checker Examples

Config file edit

Compare two .env or nginx snippets. A single changed value shows as a change row with the old and new tokens highlighted.

Ignore whitespace

A re-indented block often lights up red and green. Turn on Ignore whitespace to treat "foo bar" and "foo bar" as the same line.

Ignore case

When casing is the only difference (Hello vs hello), Ignore case keeps the line marked unchanged so real content edits stand out.

Copy unified diff

The Copy diff summary button writes Similarity / Added / Removed / Changed counts plus a Git-style --- / +++ patch you can paste into chat or a ticket.

Frequently Asked Questions about Diff Checker

Is my text uploaded to a server?: No. The comparison runs only in your browser with a plain longest-common-subsequence (LCS) algorithm. Nothing is sent, logged, or stored - so configs, logs, and contracts stay on your device.
How is this different from Diffchecker or Text-Compare?: Many popular online diff sites upload your text to their servers (even over HTTPS). This page never uploads. You also get free ignore-whitespace, ignore-case, hide-unchanged, word-level highlights, and a copyable unified diff without an account.
What does Ignore whitespace do?: It normalizes runs of spaces and tabs and trims each line before comparing. Useful when one side was reformatted or when Windows vs Mac line pastes changed indentation.
What is a changed line versus added or removed?: When a removed line sits next to an added line, the tool pairs them as a change and runs a second word-level LCS so you see which tokens moved. Pure inserts and deletes stay as added or removed.
How is similarity calculated?: Similarity is based on how many lines the LCS shares relative to both sides: (2 × shared lines) ÷ (left lines + right lines), shown as a percentage. Identical texts score 100%.
Is there a size limit?: Yes. Each side is capped at 4,000 lines so the browser LCS table stays responsive. For larger files, compare a section at a time or split the file.

Remove Duplicate Lines

Remove duplicate lines from lists, logs, emails, or any multiline text online. Keep the first occurrence, choose case-sensitive matching, and copy the unique lines instantly.

Sort Text Lines

Sort lines of text A to Z or Z to A instantly. Free online text sorter with case-sensitive and empty-line options - runs in your browser, no signup.

JSON Minifier & Formatter

Free online JSON minifier and formatter. Minify JSON to shrink payloads or beautify (pretty-print) JSON with 2-space indentation. Validates as you go - no upload required.