Text Diff Checker

Compare two drafts

1. Paste or type the earlier version into Original text and the later version into Updated text. Both fields may be empty. Use example fills two short drafts and waits for you to select Compare.
2. Select Compare to start a local browser worker. Keep each side within 100000 UTF-16 units, 2000 line records and 10000 content units per line. Editing, Clear or Cancel stops the current comparison; your drafts are not silently shortened.
3. Read the match or difference status, added/removed/unchanged counts and numbered rows. Show whitespace and controls reveals otherwise hard-to-see changes. Previous and Next expose every result row; no file is uploaded or merged.

Understand exactly what is compared

CRLF and standalone CR line endings become LF before comparison. Browser text fields already normalize line endings, so a match does not establish byte-identical source files or recover the clipboard's original line-ending convention.

A line record includes its final LF when one exists. The text a and the text a followed by LF each contain one record, but those records differ. Empty text has no records; one LF represents one blank record.

Everything else remains significant, including trailing spaces, tabs, nonbreaking spaces, letter case and different Unicode combining sequences. Similar-looking text may differ. A wrapped line on screen is not another record, and the input limit counts UTF-16 units rather than visible characters.

A completed comparison finds a shortest whole-line insertion/deletion script. Repeated lines can admit several equally short alignments. Removed and added rows do not uniquely identify a rewritten or moved passage, and no word-level, semantic or correctness conclusion follows.

Examples of lines and endings

Compare red then blue with red then green, with both drafts ending in LF. Red is unchanged; blue is removed and green is added. Each draft has two records, with one added, one removed and one unchanged line in the comparison.

Compare a without a final newline against a followed by LF. The result has one removed and one added record, not an unchanged line plus an invented empty line. The final-LF flags read No and Yes.

Compare empty text against one LF. The result adds one blank line; the original final-LF flag is Not applicable. By contrast, two empty drafts match with zero added, removed and unchanged records after you explicitly select Compare.

Limits and incomplete comparisons

Input limits are inclusive and are checked without truncation. Highly different drafts can still reach an internal edit or time budget within those limits. Comparison limit reached means no complete result exists; it must not be read as a match.

An unavailable worker, cancellation or failure preserves the drafts but produces no comparison result. Try again explicitly or use smaller drafts. No fallback blocks the page by running the diff on its main thread, and background browser scheduling prevents a guaranteed completion deadline.

This tool accepts pasted plain text, not PDF, Word or other document files. It does not ignore whitespace or case, validate facts or code, approve safety-critical instructions, apply a patch, merge changes or create a saved/shared report.

Local text processing

The comparison runs in a dedicated browser worker. The tool does not upload drafts or results, put them in URLs, include them in logs or analytics, or save them in browser storage. Ordinary site and asset requests still occur. User text is rendered as text, not executed as HTML or code.