There's an irony in most "paste your config to check for leaked secrets" web tools: pasting a secret into a random website is the leak. You're trusting a server you can't see.
So I built devguard-scan the other way around — it runs 100% in your browser, zero dependencies, and makes no network calls at all.
Don't take my word for it. Open DevTools → Network, scan a file, and watch zero requests fire. The source has no fetch, XMLHttpRequest, WebSocket, or sendBeacon — grep it yourself. It can't exfiltrate what it never calls.
The 10 detection rules (OpenAI, AWS, GitHub classic + fine-grained PAT, Stripe, Google API, Slack token + webhook, private-key blocks, generic assignments) aren't a weaker JS port — they're the exact regex set from a canonical Python scanner, parity-checked byte-for-byte so the convenience of "in-browser" doesn't cost you detection coverage.
It's a POC, MIT-licensed, and open to rule-requests: github.com/WRG-11/devguard-scan
The broader point: for a security tool, "trust me" isn't good enough. The design should make the safety property verifiable by the user — here, an empty Network tab. What other dev tools should be provable rather than promised?