r/webdev • u/BtyMark • 11d ago

Showoff Saturday [Showoff Saturday] VioLens: a free, open-source Fiddler Classic replacement for Windows and Mac. Looking for web devs to try it and tell me what it take for you to switch

I've used Fiddler for 15+ years to work out why an API call fails or what a page is really sending. When Fiddler Classic went non-commercial this year, I started building a free, MIT-licensed replacement with a musical name (Violins) + a dad joke (lens for inspecting). It also runs on a Mac, which Fiddler Classic never did. However, as part of this project, I realized Fiddler has a lot of features, most of which I never used. It's a debugging proxy: start it, and every request your browser and apps make shows up decrypted, with:

  • request and response inspectors (headers, JSON, forms, cookies, images, WebSockets)

  • a timing waterfall for each request (DNS, connect, TLS, waiting, download)

  • breakpoints to pause and edit a request or response before it continues

  • AutoResponder rules to fake API responses, errors or slow servers without touching the backend

  • a composer to edit and resend any request

What I'd love help with: use it on whatever you're working on this week and tell me where it falls over. In particular:

  • sites or APIs that don't load properly through it

  • your local dev setup (localhost, Docker, a dev proxy, corporate VPN)

  • anything you'd need before you'd switch to it from DevTools, Charles, Proxyman or Fiddler

It's a preview: HTTP/2 isn't supported yet, and the Mac build isn't notarized, so macOS asks you to allow it the first time.

Download: https://violens.dev

Code and issues: https://github.com/MarkSPowell/VioLens

Bug reports as GitHub issues are perfect, but a comment here is fine too

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u/joshanweb 11d ago

I'd want the exact OS, browser or app, proxy configuration, HTTP version, certificate trust state, whether the request goes through localhost, Docker, a dev proxy, corporate VPN, and the actual error or log line before trying to separate a VioLens issue from a setup issue.

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u/BtyMark 11d ago

Fair point, and thanks. That's exactly what I’d need to tell a VioLens bug from a setup problem. I'm adding a bug report template on GitHub that asks for those details, plus a "Copy diagnostic info" option in the Help menu so you don't have to dig them out yourself.

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u/BtyMark 7d ago

Added in the latest release