10 Developer Tools You Didn't Know You Could Run Entirely in Your Browser

Every developer has a handful of tasks that interrupt their flow — decoding a JWT from a staging environment, formatting a messy JSON API response, figuring out what a cron expression actually means. You Google it, click the first result, and hope the sketchy-looking site does not steal your data. Here are 10 common developer tasks you can handle entirely in your browser — no installs, no server requests, no data leaving your machine. I have been using DevToolbox for these, which runs everything client-side. 1. Format and Validate JSON The scenario: You hit a REST API and get back a 400-character single-line JSON blob. You need to find a nested field buried three levels deep. Instead of piping through python -m json.tool in the terminal, paste it into a JSON Formatter . You get syntax highlighting, collapsible nodes, and instant validation. If the JSON is malformed, it tells you exactly where the error is. Pro tip: This is especially useful when debugging webhook payloads — Stripe, Git