SwissDev.tools Dev Helper

Network profiling, rewrite/proxy/mock/CSS rules, and watchdog alerts for any site — plus a CORS-bypass relay for swissdev.tools.

SwissDev.tools Dev Helper is a network debugging toolkit for developers. It lets you: - Rewrite URLs and override request/response headers, compiled into Chrome's declarativeNetRequest engine. - Proxy matching traffic through a server you configure. - Mock API responses locally by intercepting fetch() calls — no backend required to test error states, empty states, or unreleased API shapes. - Inject a CSS stylesheet into matching pages — an absolute URL or a bundled extension asset. - Watch for a matching request completing — a webhook landing, an intermittent error — and get a desktop notification the moment it happens, without babysitting the Network tab. - Profile which domains are consuming the most cumulative request time. Works standalone on any site you're developing against. It also pairs with swissdev.tools — a free collection of browser-based dev tools (JSON, JWT, HTTP client, and more) from the same developer — relaying that site's requests past CORS and mixed-content restrictions when you're testing against your own local or dev servers. All rules and captured data stay on your device — this extension doesn't collect, transmit, or sell any data. See the privacy policy for details.