Building a Zero-Server-Cost, 100% Client-Side Utility Toolbox (And Why You Should Stop Uploading API Keys to Random Sites)

Hi DEV community! 👋 As developers, we’ve all been there: You have a massive, unformatted JSON payload from a wonky API, or you need to quickly extract an image from a client's PDF. You Google "JSON Formatter" or "PDF to Image", click the first result, paste your data, and hit format. But recently, I had a terrifying realization while debugging a production issue. I was about to paste a JSON payload containing live customer emails and active API keys into a random ad-riddled website. How insane is it that we routinely hand over highly sensitive production data to remote servers just to make a string readable? I wanted a utility suite that actually respected data privacy. So, I spent a few weekends building Mini-Tools.uk — a 100% offline-capable, client-side only toolbox. 🛠️ The Technical Challenge: Doing Everything in the Browser My main constraint was strict privacy: absolutely zero backend processing . Every single tool had to run inside the user's DOM. Here is how I tackled a few of