About this tool
Why it exists
This tool was built to solve a specific problem: every convenient online text comparison tool sends your text to a server.
That is a perfectly sensible way to build a web app, and for most content it does not matter. But the moment you need to compare two versions of a contract, an unpublished manuscript, an exported customer list or a medical record, uploading it to a third-party service stops being acceptable. The usual alternatives are worse: install a desktop diff tool, learn a command-line utility, or read both versions manually and hope you spot the change.
Modern browsers are fast enough to do this work themselves. So this tool does the entire comparison locally, in JavaScript, on your own machine. No API, no upload, no server-side processing, no logs.
How you can verify the privacy claim
Claims about privacy are easy to make and hard to trust, so here is how to check this one yourself:
- Open the comparison tool.
- Open your browser's developer tools (F12, or right-click → Inspect).
- Switch to the Network tab.
- Paste text into both panes and press Compare.
You will see no request carrying your text. The only network activity on the page is loading the page itself and, if enabled, analytics and advertising scripts — none of which receive your input. Analytics records that a comparison ran and roughly how large the input was; it never records what you compared.
What it does
Side-by-side and unified comparison views. Character, word and line level granularity. Options to ignore whitespace, letter case and blank lines. Local file reading for plain text, Markdown, CSV, TSV, JSON, XML, HTML, log, YAML and common source formats. Copy and download of results. Dark mode. Full keyboard operation.
No account, no usage limit, no watermark, no paid tier.
What it deliberately does not do
There is no way to save a comparison or share it by link. Both would require storing your text on a server, which would break the one property that makes this tool worth using. If that trade-off does not suit your use case, a server-based tool is genuinely the better choice — this one is not trying to be everything.
Word and PDF comparison are not supported yet either. Those formats are compressed and structured, so comparing raw bytes is meaningless; proper support needs a parser. It is on the list. In the meantime, copying the text out and pasting it in works.
How it is paid for
Because the comparison runs on your device, running this site costs almost nothing — there are no servers doing the computation. It is supported by advertising rather than by charging users or metering usage. Ads are kept out of the tool interface itself; if an ad ever obstructs the comparison area, that is a bug worth reporting.
Built with
Astro for static site generation, Tailwind CSS for styling, and the
diff library for the comparison algorithm. Hosted on Cloudflare Pages.
The comparison engine is covered by an automated test suite including checks that no
network call can be introduced into it.
Contact
Bug reports, feature requests and corrections are all welcome — see the contact page. If a comparison produces a wrong result, a reproducible example is the most useful thing you can send.
Text Compare Checker — textcomparechecker.com