Topic cluster
Proxy tools
Free browser-side tools for proxy engineering: client IP resolution, no_proxy matching, nginx proxy_pass rewriting, PROXY protocol decoding, PAC testing.
Six tools for the parts of proxy configuration that are easy to get subtly wrong and hard to verify by reading. All of them run entirely in your browser: no request is made, nothing is uploaded, and nothing is stored.
They exist because each one answers a question that otherwise requires deploying a change to find out.
| Tool | Answers |
|---|---|
| Client IP resolver | Which address in this X-Forwarded-For chain is really the client, given my trusted proxies? |
| no_proxy tester | Will curl, Go, Python and Java all agree that this URL bypasses the proxy? |
| nginx proxy_pass simulator | What upstream URI does this location and proxy_pass pair actually produce? |
| PROXY protocol decoder | What do these header bytes mean, and is the length field consistent? |
| PAC file tester | What does FindProxyForURL return for this URL, and how many DNS lookups did it cost? |
| Timeout ladder checker | Which hop in my chain gives up first, and is my ladder inverted? |
Each tool page also explains the rule it implements, so the tool is checkable rather than something you have to take on faith.
Every tool in this cluster#
- Client IP resolver (X-Forwarded-For and trusted proxies)Paste an X-Forwarded-For chain, a socket peer address and your trusted proxy CIDRs, and see exactly which address your stack should treat as the client.
- nginx proxy_pass URI simulatorEnter a location, a proxy_pass value and a request URI, and see the exact upstream request nginx will make, plus the trailing slash trap that changed it.
- no_proxy tester across curl, Go, Python and JavaOne NO_PROXY string, five implementations. See which clients bypass the proxy for a given URL and which do not, with the matching rule that decided it.
- PAC file testerRun a proxy auto-config file against any URL in your browser, see the return value, every helper call it made, and which of those calls cost you a DNS lookup.
- PROXY protocol decoder (v1 and v2)Paste hex bytes or a v1 text header and get a field by field decode, including TLVs, TLS details and the length checks that catch a malformed sender.
- Timeout ladder checkerEnter the timeouts and retry counts for every hop in your chain and see which one gives up first, what the user sees, and where the ladder is inverted.