HTTPS Fallback Proxy is a lightweight HTTP proxy for connecting to HTTPS endpoints that only support older TLS/SSL protocol versions.
When it receives a request for an HTTPS destination, it attempts the handshake in the following order, retrying with the next version whenever one fails:
TLS 1.2 → TLS 1.1 → TLS 1.0 → SSL 3.0 → SSL 2.0
Modern TLS libraries and operating systems have dropped or disabled most legacy protocols by default. Some old systems, embedded devices, industrial equipment and legacy applications still expose HTTPS services that can't negotiate a modern protocol — this proxy acts as a compatibility layer so a modern client can still reach them, without having to be configured to understand every obsolete protocol itself.
Industrial and embedded equipment. PLCs, IoT gateways, network cameras, printers or building-management systems whose firmware hasn't been updated in years and only speaks TLS 1.0 or SSL 3.0.
Legacy internal APIs and integrations. Old ERPs, billing systems, or third-party services that a client team can't force onto modern TLS, but that your application still needs to talk to.
Migration and decommissioning projects. A staging step while planning an upgrade: keep the legacy service reachable through the proxy while you validate that a newer TLS-compliant replacement works, before switching over for good.
Security research and protocol analysis. Studying how obsolete protocols negotiate, fail, or can be downgraded, in a reproducible, isolated setup instead of against production systems.
Interoperability and regression testing. Verifying that a service, library, or client still behaves correctly against older TLS/SSL versions, e.g. as part of a test suite for software that must support legacy customers.
Debugging handshake failures. Diagnosing exactly which protocol version a mysterious legacy endpoint expects, by observing which fallback step succeeds.
Isolated or air-gapped systems. Hardware that physically cannot be patched or replaced in the short term (e.g. certified medical or industrial devices) but still needs occasional connectivity from modern tooling.