Compare two texts

A diff checker is how you see what actually changed between two versions of a thing you already have: a contract clause, a price list, a config file, a blog draft, two CSV exports from the same database a week apart. Cloud diff sites ask you to upload both files, which is a strange request when the content is a customer list or an unpublished manuscript. imissfiles compares them in this tab. Original on the left, changed on the right, or a unified view on a narrow screen. Nothing is posted, stored, or queued.

Line-level diff is the easy half. The half that separates a real tool from a toy is word-level highlighting inside a changed line. If you fix a single amount on an invoice, you should see that amount light up — not a red line deleted and a green line added as if the whole sentence were new. We run a Myers longest-common-subsequence pass on lines, then a second Myers pass on the words of paired lines. Added lines get a green tint and a + gutter. Removed lines get a red tint and a − gutter. Color is backup; the symbols work if you cannot see the tint.

Real files are mostly unchanged. Collapse runs of more than ten identical lines behind a “show 47 unchanged lines” control or a 4,000-line log is unusable. Ignore whitespace when one export padded columns and the other did not. Ignore case when you are looking at titles. Ignore blank lines when a Word paste inserted empties. Word wrap is a display toggle; it does not change the comparison. The stats bar reports additions, deletions, unchanged lines, and a similarity percent: two times the unchanged count, divided by the sum of both lengths. 96% similar means the files share most lines, not that they are legally identical.

You can paste, or drop .txt, .md, .json, .csv, .log, and other plain-text files. Two Word documents are not a text diff until you extract them: convert each to text with PDF to Text (from a PDF) or copy from Word, then paste. We do not parse .docx here on purpose — that is a different engine. Copy the result as unified diff, download it as .txt, or download an HTML snapshot with the colors preserved for email. Load the example if you want to see a one-word and one-line change before using your own files.

Use Diff Checker when a teammate says “I only changed the header” and you would like proof. Use it when two CSV dumps should match and do not. Then jump to Find and Replace to fix a systematic typo, or Word Counter if the draft also has a length cap. Related extractors: PDF to Text, Image to Text, OCR PDF. The comparison never leaves this device, which is the only reason we are comfortable putting it next to ads.