Text Diff Checker - Online Compare & Find Differences

Our tool uses the Longest Common Subsequence (LCS) algorithm to compare two texts line by line. It identifies lines that were added, removed, or modified, then displays them with color-coded highlights. For modified lines, it performs a secondary character-level comparison to pinpoint exactly which characters changed within the line.

Side-by-Side view displays both texts in two columns with aligned line numbers — ideal for visually comparing versions side by side. Unified view shows all changes in a single column with + and - markers (similar to Git diff), making it easier to read the overall change log in a linear fashion.

Yes, the tool handles texts with up to 3,000+ lines efficiently. The algorithm runs entirely in your browser — no data is sent to any server. For extremely large files (5,000+ lines), you may experience a brief processing delay. In such cases, we recommend splitting the comparison into smaller sections.

Absolutely. All text comparison is performed locally in your browser using client-side JavaScript. Your data never leaves your device, is never transmitted over the network, and is never stored on any server. This makes the tool safe for comparing sensitive documents, code snippets, or confidential text.

Ignore Case treats uppercase and lowercase letters as identical (e.g., "Hello" = "hello"). Trim Whitespace removes leading and trailing spaces from each line before comparison, so formatting differences in indentation or trailing spaces are ignored. Skip Blank Lines excludes empty lines entirely from the comparison.

When two lines are identified as a potential modification (rather than a full deletion + addition), the tool runs a secondary LCS algorithm at the character level. This precisely identifies which characters were removed (shown with a strikethrough on red) and which were added (highlighted in green), giving you a clear, granular view of the exact changes.