Paste two versions of any text or code and instantly see exactly what was added, removed and changed. Switch between line-level and word-level views to catch every edit — all computed privately in your browser. There is no signup, no upload and no limit, so you can compare drafts, contracts, configs and code as often as you like.
Differences (line view)
The quick brown fox jumps over the lazy dog. Version control keeps a history of every change. Always proofread before you publish.The quick brown fox leaps over the sleepy dog. Version control keeps a complete history of every change. Always proofread carefully before you publish. Reviewing diffs saves hours of debugging.
Why
When two versions of the same document drift apart — a contract that came back from legal with tracked changes turned off, a paragraph a colleague quietly rewrote, a config file that suddenly stopped working — the hardest part is rarely fixing the problem. It is finding it. Reading two long blocks of text side by side and spotting the one word, one number or one missing line that actually changed is slow, error-prone and exhausting, and human attention naturally glosses over text that looks familiar. A text diff checker does that comparison for you in milliseconds, painting every addition, deletion and edit in color so the differences jump off the page instead of hiding in plain sight. What might take ten careful minutes of cross-reading becomes a two-second scan.
Diffing is the quiet engine behind a huge amount of modern work. Every commit in Git, every "track changes" mark-up in a word processor, every code review on a pull request, every contract redline and every database migration review is, at its core, a comparison between a before and an after. Our tool brings that same power to any text you can paste, with no repository, no account and no setup. You get a line-level view that mirrors how version-control systems think about changes, and a word-level view that zooms in to show exactly which words inside a line were swapped — perfect for proofreading prose, where a whole-line diff would flag an entire sentence as changed even when a single adjective was edited.
The two view modes exist because "what changed" means different things in different contexts, and choosing the right granularity is the difference between a diff that helps and one that overwhelms. In source code, structured data and configuration files, the line is the natural unit: you want to know which lines were inserted, which were deleted, and whether a block moved. The line view collapses everything else and leaves you with a clean, Git-style summary of edits. In prose, contracts and copy, the sentence rarely changes wholesale — a tense is fixed, a number is corrected, a clause is softened. The word view treats whitespace-delimited tokens as the unit and underlines exactly those micro-edits, so you read the change rather than re-reading the paragraph.
Speed and clarity only matter if you can trust where your text goes, and this is where an in-browser diff checker quietly outperforms many online alternatives. The comparison runs entirely inside your browser using a well-tested open-source diffing algorithm; the text you paste is never uploaded, logged or transmitted to a server. That distinction is not academic. When the content is an unsigned contract, an embargoed press release, customer records, a patient note or proprietary source code, pasting it into a tool that ships your data to a remote backend can breach an NDA or a compliance policy. Here there is nothing to install and nothing to trust beyond the page already loaded in front of you — you could disconnect from the internet and the diff would still work.
A diff checker is also a verification tool, not just a viewing tool, and that reframing is what makes it useful day to day. It is one thing to ask someone to "make the edit"; it is another to confirm the edit was actually made, and only that edit. Paste the version you sent and the version you got back, and the highlighting answers three questions at once: was the requested change applied, were any unrequested changes slipped in, and did anything that should have stayed the same accidentally move. That same logic applies to AI-generated rewrites, auto-formatters, find-and-replace operations and bulk edits — any process where you trusted a tool or a person to touch some text and now need objective proof of exactly what they touched.
Finally, a good diff tool earns its place by being instantly available with zero friction, which is exactly when people actually use one. Most comparisons are not planned; they happen the moment you sense something is off — a build broke, a clause reads differently, a translation lost a sentence. If checking requires installing software, opening a repository or signing into an account, most people skip it and squint instead, which is precisely how small but costly differences slip through. Because this checker is free, requires no signup and loads as a single page, it is realistic to reach for it dozens of times a week for tiny, throwaway comparisons. That low cost of use is the whole point: the easier it is to verify, the more often verification actually happens.
How
Drop the original text or code into the left field and the changed version into the right field. Anything works — prose, JSON, source code, CSV rows, log output or plain notes — and you do not need to clean up formatting first. The comparison runs the instant you stop typing, so there is no separate button to press.
Use the line view to see which whole lines were added or removed, which is ideal for code, config files and structured data where the line is the meaningful unit. Switch to the word view to highlight the individual words that changed inside a sentence, which is ideal for editing and proofreading prose. You can flip between the two on the same pair of texts to view a change at both altitudes.
Green marks additions, red marks deletions (struck through in word view), and unchanged text stays black, while a running tally shows how many segments were added and removed. Use Swap to flip the two sides when you pasted them in the wrong order or want to read the change from the opposite direction, or Clear to empty both fields and start a fresh comparison.
Who
Compare two snippets, config files or function versions outside of a repository — handy for reviewing a pasted patch, checking what an AI assistant rewrote, or confirming a one-line fix before committing it. The line view mirrors how Git presents changes, so it doubles as a lightweight code-review pane when you do not have a full diff tool open.
See exactly which words an editor or co-author changed in a draft, verify that a requested revision was actually applied, and proofread two versions of a paragraph without re-reading both top to bottom. The word view is especially useful for catching subtle edits like a changed tense, a dropped negation or a swapped figure that a quick read would miss.
Spot every altered clause, figure or term between two versions of a contract, policy or spreadsheet export — the kind of single-character change that is dangerous to miss and tedious to find by eye. Because nothing is uploaded, sensitive agreements and financial data stay on your machine while you redline them.
Check what a supervisor or reviewer changed in a thesis chapter, compare a quotation against its source for accuracy, or confirm that two datasets or interview transcripts match line for line before relying on them. It is also a fast way to verify that your own revisions actually addressed each comment.
Compare an updated source string against the previous version to see exactly which parts of the original changed, so you only re-translate what is new instead of redoing a whole block. Diffing two translations of the same passage also helps reconcile competing wording during review.
Place two log files, API responses or error outputs side by side to isolate the line that differs between a working and a failing run. When reproducing a bug, a diff of "expected" versus "actual" output points straight at the divergence instead of forcing you to scan both dumps manually.
When
Whenever a document comes back from someone else and you need to know precisely what they touched, a diff turns a guessing game into a quick scan of the highlighted changes. This is essential when "track changes" was never turned on and the edits are otherwise invisible.
Before committing, when reviewing a teammate’s snippet, or after an editor auto-formats a file, diffing confirms that only the intended lines changed and nothing slipped in by accident. It is also the fastest way to separate a meaningful logic change from a wall of cosmetic reformatting.
When a language model paraphrases, humanizes or "improves" your text, a word-level diff shows exactly what it altered so you can keep the good edits and revert anything that changed your meaning. This guards against the subtle drift where an AI quietly introduces a claim or tone you never intended.
Compare two exports, environment files or API responses to find the row, key or value that differs — far faster and more reliable than eyeballing two large blocks of text. A single flipped flag or changed endpoint in a config often explains an outage, and a diff surfaces it immediately.
When a version-control merge leaves you with two competing versions of the same section, pasting both into the diff makes the conflicting lines obvious so you can decide what to keep. Seeing the changes in color is often clearer than parsing raw conflict markers in an editor.
Place a suspect passage next to a possible source to see how much overlaps verbatim and where the wording was lightly altered to disguise it. The word view reveals the tell-tale pattern of a few swapped synonyms around an otherwise identical sentence.
Paste two versions of any text or code and instantly see exactly what was added, removed and changed. Switch between line-level and word-level views to catch every edit — all computed privately in your browser. There is no signup, no upload and no limit, so you can compare drafts, contracts, configs and code as often as you like.
Use the Text Diff Checker