What this diff shows
This text compare tool takes two blocks of text — an original and a changed version — and shows exactly what moved between them. Paste the first version on the left, the second on the right, and the Differences panel below updates as you type. Text that appears in both versions renders as plain text. Text that only exists in the changed version is highlighted as an insertion. Text that only exists in the original is struck through, marking it as a removal. Nothing is summarized or guessed at: every character you see in the output came directly from one of the two boxes you pasted into, so you can trust the diff checker online result as a literal record of what changed, not an approximation of it.
Word mode vs. line mode
The mode switch above the two boxes controls the granularity of the comparison, and picking the right one makes a real difference in how readable the result is. Word mode breaks both texts into words and punctuation, then compares those pieces — the natural choice when you want to compare two texts online at the sentence or paragraph level, like an edited email, a revised paragraph, or two drafts of a product description. A single reworded phrase shows up as a small, precise highlight instead of an entire sentence turning red. Line mode instead treats each line as one unit, comparing the texts line by line the way source control tools do. That's the better fit for anything organized in rows: a bulleted list, a CSV-style export, a configuration file, or a short code snippet, where you want to know which whole lines were added, removed, or left untouched rather than which individual words shifted around inside them. If a result looks noisier than expected — long stretches highlighted for what feels like a minor edit — switching modes usually clears it up immediately.
How to compare two texts
Using the tool takes three steps. First, paste the original version of your text into the "Original text" box on the left. Second, paste the revised or changed version into the "Changed text" box on the right — order matters, since removals are always shown relative to the original and additions relative to the changed text. Third, choose word or line mode with the radio buttons above the boxes; the default is word mode, which suits most prose. The Differences section updates live as you type or paste, so there's no button to press and no page to reload. If you paste a new version into either box, the highlighted output recalculates immediately. Because the comparison runs entirely in JavaScript in your browser, there's no upload delay and no server round-trip, even for a fairly long document — you'll see the highlighted result appear within a fraction of a second of pasting.
Common uses: contracts, essays, code snippets
A text difference checker is useful anywhere two versions of the same document need to be reconciled. For contracts and legal documents, line mode or word mode both help confirm that a redlined draft matches what was actually agreed — spotting a quietly deleted clause or a changed dollar figure that's easy to miss by eye. For essays, blog posts, or any prose that's gone through an editing pass, word mode shows precisely which phrases were tightened, cut, or added, which is faster than rereading the whole piece side by side. For code snippets, short configuration blocks, or command-line output, line mode mirrors what a version control diff would show, making it easy to confirm that a copy-pasted change matches what you intended before you commit it elsewhere. In every case, the appeal is the same: instead of scanning two blocks of text for differences by eye, which is slow and unreliable for anything beyond a sentence or two, this text compare tool does the comparison for you and shows the result as color-coded, unambiguous highlights.