### [Fast Fallback](https://square.github.io/okhttp/4.x/okhttp/okhttp3/-ok-http-client/-builder/fast-fallback/)

Since version 5.0, `OkHttpClient` supports fast fallback, which is our implementation of Happy Eyeballs [RFC 6555](https://datatracker.ietf.org/doc/html/rfc6555).

With fast fallback, OkHttp attempts to connect to multiple web servers concurrently. It keeps whichever route connects first and cancels all of the others. Its rules are:

 *  Upgrade: [Okio 3.7.0][okio_3_7_0].


## Version 5.0.0-alpha.11

_2022-12-24_

 *  New: Enable fast fallback by default. It's our implementation of Happy Eyeballs,
    [RFC 8305][rfc_8305]. Disable with `OkHttpClient.Builder.fastFallback(false)`.
 *  Fix: Don't log response bodies for server-sent events.
 *  Fix: Skip early hints (status code 103) responses.

    /**
     * Configure this client to perform fast fallbacks by attempting multiple connections
     * concurrently, returning once any connection connects successfully.
     *
     * This implements Happy Eyeballs ([RFC 6555][rfc_6555]), balancing connect latency vs.
     * wasted resources.
     *
     * Defaults to enabled, call with [fastFallback] = false to revert to 4.x behaviour.
     *