Text Diff Checker

Paste two versions of anything — a config file before and after an edit, two drafts of a paragraph, yesterday's log next to today's — and this checker lines them up and marks exactly what changed. Removed lines turn red, added lines green, edited lines amber, and everything untouched stays grey, so a 200-line file with two real changes reads in a glance instead of a squint.

The comparison is line by line, shown inline or side by side, and it runs entirely in your browser. Two switches handle the differences that usually trip people up: Ignore whitespace, so re-indentation or trailing spaces don't bury the real change, and Ignore case. Nothing you paste is uploaded — the whole diff happens on your machine, which matters when the "text" is a production config or an unreleased draft.

What "line by line" actually means. The tool walks both texts, matches the lines that are identical, and flags the gaps: a line only on the left is a removal, a line only on the right is an addition, and a line that changed in place is a modification. It's the same idea behind Unix diff and Git — find what's common, mark the rest — kept deliberately line-oriented.

What that means in practice:

- It compares whole lines, not words. Change one word in a long line and the entire line is marked modified; you'll see the old and new versions, but not the single word underlined. For word-by-word prose comparison that's a real limitation — see the FAQ.
- A moved block isn't detected as a move. Cut ten lines from the top and paste them at the bottom and you'll see ten removals and ten additions, not "moved." No plain line-diff tracks moves.
- Ignore whitespace collapses runs of spaces and tabs to a single space before comparing, so reformatting (re-indenting a block, tabs → spaces) stops registering as a change. Leave it off when whitespace is the thing you're auditing.

The counts at the top — added, removed, modified, unchanged — are the fast sanity check. Expecting a one-line edit but seeing "+40 −38"? That's almost always line-ending noise, not real changes.

vs git diff. Git compares tracked files inside a repository from the command line and produces an appliable patch. This tool is for the ad-hoc case: two blobs of text you have in your clipboard, no repo, no terminal, nothing to commit. Different jobs.

vs Word / Google Docs track changes. Those track edits live inside one document, word by word, with authorship and comments — the right tool for collaborative prose. This is a neutral, throwaway side-by-side for any two versions, with no document to own.

vs desktop tools (Meld, Beyond Compare). Those do folder comparisons, three-way merges, and word-level highlighting. Reach for them on a whole project. Reach for this when you just need a fast, zero-install, nothing-uploaded look at two snippets.

Line-level vs word-level. This is line-level on purpose — it's the natural unit for code and configs. If you're comparing paragraphs of prose and need the exact changed word, a word-diff or track-changes will serve you better.