<!--
{
  "availability" : [
    "iOS: 12.0.0 -",
    "iPadOS: 12.0.0 -",
    "macCatalyst: 13.1.0 -",
    "macOS: 10.14.0 -",
    "tvOS: 12.0.0 -",
    "visionOS: 1.0.0 -",
    "watchOS: 5.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Security",
  "identifier" : "/documentation/Security/sec_protocol_options_set_tls_is_fallback_attempt(_:_:)",
  "metadataVersion" : "0.1.0",
  "role" : "Function",
  "symbol" : {
    "kind" : "Function",
    "modules" : [
      "Security"
    ],
    "preciseIdentifier" : "c:@F@sec_protocol_options_set_tls_is_fallback_attempt"
  },
  "title" : "sec_protocol_options_set_tls_is_fallback_attempt(_:_:)"
}
-->

# sec_protocol_options_set_tls_is_fallback_attempt(_:_:)

```
func sec_protocol_options_set_tls_is_fallback_attempt(_ options: sec_protocol_options_t, _ is_fallback_attempt: Bool)
```

## Parameters

`options`

A `sec_protocol_options_t` instance.

`is_fallback_attempt`

Set a flag indicating that this is a TLS fallback attempt.

## Discussion

\abstract Signal if this is a TLS fallback attempt.

```
 A fallback attempt is one following a previously failed TLS connection
 due to version or parameter incompatibility, e.g., when speaking to a server
 that does not support a client-offered ciphersuite.

 Clients MUST NOT enable fallback for fresh connections.
```

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)