I built an embeddable screen-time calculator that doesn't phone home
Most embeddable widgets are surveillance with rounded corners. You paste one script tag, it opens a socket back to someone else's server, drops analytics, fingerprints the page, and turns your article into their funnel. I wanted the opposite. I had built a small screen-time calculator for an iPhone side project. You enter daily phone hours, how much of that time you'd actually want back, and your age. It returns the number not just as hours per year, but as waking years of the life you have left . The surprising part was not the maths. The surprising part was that the calculator itself was the first marketing asset I had built that people might reasonably link to. So the next step was obvious: make it embeddable. Constraints I gave myself four rules: No tracking script No backend callback No cookie or storage requirement Useful standalone, but with a real reason to click through That ruled out the normal widget pattern immediately. I did not want a script that asks the host page for DOM access. I did not want the embed to send typed values back to me. And I did not want to bolt analytics onto a tool whose whole public claim is "nothing leaves your device". So the widget became a single static iframe page. The embed snippet This is the whole thing: <iframe src= "https://shantj.github.io/sproutguard/embed.html" width= "100%" height= "620" style= "border:0;max-width:600px" loading= "lazy" title= "Screen time calculator" ></iframe> <p style= "font-size:13px;opacity:.7;margin:6px 0 0" > <a href= "https://shantj.github.io/sproutguard/screen-time-calculator.html?ct=embed-credit" > Screen Time Calculator </a> — free, no signup, runs in your browser. </p> No JavaScript include. No SDK. No npm package. Just an iframe and a credit link. The iframe points at a page that contains the calculator UI and the arithmetic. Because it is a static page, the host site never has to trust my script with its DOM. The actual calculator logic The core number is intentionally boring: const LIF