Text diff checker
Paste an original and a changed version and instantly see what is different. Additions and removals are highlighted in color, line by line or word by word, with a count of each — all without uploading your text.
How to use Text Diff Checker
- 1
Paste the original
Put the first version of your text in the left box.
- 2
Paste the changed version
Put the second version in the right box.
- 3
Choose line or word mode
Compare by whole lines for structured text, or by word to pinpoint edits within similar text.
- 4
Read the highlighted diff
Additions and removals are color-coded, with a count of each shown above the result.
See exactly what changed between two versions
Comparing two versions of text by eye is genuinely hard. A single changed word in a long paragraph, a moved line, or an extra space can be almost invisible when you are reading two blocks side by side and trying to hold both in your head. A diff checker removes the guesswork by computing the differences for you and showing them in color: text that was added appears one way, text that was removed appears another, and everything that stayed the same is dimmed so the changes stand out. In1 also shows a count of additions and removals, giving you an instant sense of how big the change really is. Instead of squinting back and forth and hoping you have spotted everything, you get a clear, reliable map of every difference between the two versions, which is exactly what you need when accuracy matters and a missed change has consequences.
Compare by line or by word
Different comparisons call for different granularity, so the tool offers two modes. Line-by-line comparison treats each line as a unit and is ideal for structured text like lists, configuration, code, addresses or anything where the line is the meaningful chunk — it tells you which whole lines were added, removed or left alone. Word-by-word comparison drills deeper, highlighting the specific words that changed within otherwise similar text, which is what you want when two paragraphs are mostly the same and you need to pinpoint the exact edits inside them. You can switch between the modes instantly and watch the highlighting change, so it is easy to start with a line-level overview to see the shape of the change and then drop to word level to examine a particular passage in detail. Having both in one tool means you do not have to choose the right granularity up front or open a separate utility.
Proofread edits and catch unintended changes
One of the most valuable uses of a diff is confirming that a change did only what you intended. When you edit a contract, a piece of copy, a configuration file or a block of code, it is easy to alter something by accident — a deleted word, a number that got changed, a line that moved. Comparing the before and after versions surfaces every difference, so you can verify that the edits are exactly the ones you meant to make and nothing slipped in unnoticed. It is equally useful in the other direction: when someone hands you a revised document, a diff shows you precisely what they touched instead of forcing you to re-read the whole thing looking for changes. This makes review faster and far more trustworthy, whether you are checking your own work, reviewing a collaborator's edits, or auditing how a piece of text evolved between two points in time.
Private by design — your text stays local
The documents people compare are frequently sensitive: contract drafts, unpublished writing, source code, configuration or confidential records. In1 computes the diff entirely in your browser using plain JavaScript, so both versions of your text stay on your own device. Nothing is uploaded, nothing is stored and there is no account to create. The comparison runs the moment you paste or edit either side, with no server round trip, which means it is instant and works exactly the same offline as online. You can compare long documents without waiting for an upload or worrying about where your text ends up. This local-only approach is what makes a diff checker safe to use on material you would never paste into an unknown online service — you get the convenience of an instant visual comparison with the assurance that the content never leaves your machine.
Who uses a diff checker?
Diff tools started with programmers but are useful to far more people now. Developers compare versions of code, config and data to see what changed before committing or after a merge. Writers and editors check revisions, compare drafts and confirm that requested edits were applied correctly. Lawyers and contract managers compare versions of agreements to spot exactly which clauses were altered. Translators and localizers check what changed in source text so they only re-translate what is necessary. Students and academics compare drafts of essays and papers. Office workers diff two versions of a policy, a spreadsheet export or a list to find discrepancies. Anyone who has ever needed to answer the question 'what is different between these two pieces of text?' — and wanted a trustworthy answer rather than a hopeful manual scan — benefits from a fast, private diff that highlights every addition and removal at a glance, in whichever granularity the job needs. Support engineers compare a working configuration against a broken one to isolate the change that caused an outage, and editors confirm a publisher applied their corrections and nothing else. The added and removed counts give an instant sense of scale, telling you at a glance whether two versions differ by a single word or by whole paragraphs before you even start reading the highlights.
Higher limits, batch processing and an API are on the way. Want early access?