Diff checker

Use this diff checker to compare pasted drafts or text files by line, word or character. Review numbered changes together or side by side, then copy either version.

Your text never leaves the browser. No upload, storage or AI call.

Your text never leaves the browser. No upload, storage or AI call.

Drop a UTF-8 text file onto either editor. File limit: 4 MB. PDF and Word files need conversion to plain text first.

Limit: 1,000,000 UTF-16 units per text. Counts include spaces and punctuation tokens in word mode.

Ignore options

Text differences

Paste both versions, then compare. Either text can be empty.

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A diff checker finds additions and removals between two texts. Paste drafts or drop UTF-8 text files, choose line, word or character highlighting, and compare numbered results in a combined or side-by-side view. Ignore case, whitespace or line endings, hide unchanged blocks, and copy or download either original version. Everything runs locally with the Myers algorithm.

How to use this tool

Paste or open both versions
Put the earlier text on the left and the revision on the right. Drop one UTF-8 text file onto either field or use its file picker. Files are limited to 4 MB and decoded text to 1,000,000 UTF-16 units per side. Binary files and invalid UTF-8 are rejected. Empty versions are valid. Files preserve BOM and original line endings.
Choose what counts as a change
Line mode preserves final newlines. Word mode uses Unicode word segmentation, including punctuation and spaces as tokens. Character mode compares visible Unicode characters, keeping joined emoji and combining marks together. Ignore whitespace removes whitespace inside each comparison token; in word and character modes it removes whitespace before segmentation. Ignore line endings treats CRLF and CR as LF.
Read the shortest edit script
The Myers algorithm finds a shortest sequence of additions and removals for the chosen tokens. Counts include punctuation and spaces in word mode. A Web Worker keeps the form responsive and stops very difficult inputs at a work limit. Long results use paged excerpts with original line numbers. Hide unchanged blocks to focus the review, then copy or download either full input. The tool does not merge edits or store a shared result.

Myers: An O(ND) difference algorithm

Questions before you start

There is no saved comparison, share URL or merge editor. Copy or download either complete original input to use in your own editor. Downloads preserve its text, including line endings. Nothing is stored on our server.

No. Comparison runs on your device without an upload, AI call or account. Draft fields and results are excluded from session capture. Opening a source link is optional and does not send your drafts.

Repeated words and lines can have several shortest edit scripts. The tool chooses one consistent script. Additions and removals count changed tokens rather than editorial decisions, and a replacement counts as one removal plus one addition.

Yes, within the stated per-field size limit. The worker keeps the form responsive and can be cancelled by editing, clearing or swapping the texts. Highly different documents with repeated shared tokens may exceed the work limit. Compare smaller sections or try line mode if that happens.

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