Text Diff Checker - Compare Two Texts and Highlight Changes

Comparing two versions of a document by eye is slow and unreliable — a single changed word in a long paragraph, or one edited line in a hundred-line file, is easy to miss. This text diff checker automates the comparison: paste the original version and the revised version, click Compare, and every insertion and deletion is highlighted so the exact changes jump out immediately. The tool offers two comparison modes because different kinds of content call for different granularity. Line mode treats each line as the unit of comparison, producing the familiar unified-diff style output that developers know from Git and code review tools: inserted lines are shown in green with a plus prefix, deleted lines in red with a minus prefix, and unchanged lines in plain text for context. This mode shines for source code, configuration files, CSV exports, SQL statements, and any content where line structure is meaningful. Word mode instead compares individual words inside the running text, highlighting inserted words in green and struck-through deleted words in red within the flow of the paragraph. That makes it the right choice for prose: contracts, articles, emails, documentation, and translated copy, where a whole-line comparison would flag an entire paragraph for a two-word edit. Under the hood the checker uses a well-tested implementation of the Myers difference algorithm — the same approach behind most version-control systems — so the output is a minimal, sensible set of changes rather than a noisy character soup. A summary above the diff counts the changed segments, giving you an at-a-glance sense of how heavily a document was edited before you scroll through the details. Everything runs locally in your browser. Neither text is uploaded, stored, or logged, which makes the tool safe for confidential material such as legal agreements, unpublished manuscripts, internal policies, or proprietary code. Typical workflows include verifying what a colleague changed in a shared document, checking that a copy-paste between systems did not silently alter content, reviewing AI-rewritten text against the source, validating configuration changes before deployment, and confirming two exports are equivalent. If both inputs match exactly, the checker says so explicitly instead of showing an empty diff, so a clean result is never ambiguous.