About DiffStack

Who is behind DiffStack

DiffStack is built and maintained by an independent developer who kept running into the same problem: every "free" online diff tool wanted an account, uploaded files to a server, or buried the actual comparison under upsells. DiffStack is the tool we wanted to exist — open the page, paste, compare, done.

Why privacy-first

Diff tools see sensitive things: unreleased code, contracts, config files with hostnames, API responses with customer data. A tool that sends that content to a server — even briefly, even encrypted — forces you to trust someone else's infrastructure and retention policy.

DiffStack removes that decision entirely. Every comparison runs in your browser using JavaScript (the Myers diff algorithm via the open-source diff library). There is no upload endpoint for your content, no database, and no account system. Close the tab and the data is gone. Even the "Upload file" buttons read files locally with the browser's FileReader API.

How it stays free

The tools are static pages served from a CDN, so running costs are low and nothing is paywalled. We use standard, aggregate web analytics to understand which tools are used — page views only, never the content you compare. See the Privacy Policy for details.

Get in touch

Found a bug, want a new format supported, or have feedback on a tool? Contact us — feature requests from real workflows shape what gets built next.