Sourced from com.squareup.okhttp3:okhttp-bom's changelog.

Version 5.5.0

2026-08-16

This release introduces opt-in support for [Encrypted Client Hello (ECH)]. This new feature improves user privacy by encrypting domain names in transit. With regular TLS, your coffee shop’s Wi-Fi router can see that you’re visiting wikipedia.com, but it cannot see which page you’re looking at. With ECH, the router observes only the IP address. This additional privacy is most effective on sites hosted by big CDNs because the IP address doesn’t imply a particular website.

This requires ECH support in the platform’s TLS stack. Today this is only Android 17 (API 37, released June 2026). When other TLS stacks add ECH support, we'll integrate them.

ECH took a lot of work to implement because the encryption keys are published over DNS in the [HTTPS resource record], and we needed to write new code to fetch these records. This release includes a major update to OkHttp’s DNS API: it now supports multiple resource record types (not just IP addresses!), asynchronous streaming results, and in-memory caching.

To opt in, you can use DnsOverHttps:

// DnsOverHttps itself uses OkHttpClient. Build both clients upon the
// same bootstrap client so they share a connection pool and dispatcher.
val bootstrapClient = OkHttpClient()
// This sample uses Cloudflare's 1.1.1.1 DnsOverHttps service.
val client = bootstrapClient.newBuilder()
.dns(DnsOverHttps.Builder()
.client(bootstrapClient)
.url("https://1.1.1.1/dns-query".toHttpUrl())
.build())
.build()

You could also opt in with our new AndroidDns API. Unfortunately, the privacy benefits of ECH are thwarted because its DNS queries are not encrypted by default.

// AndroidDns fetches the HTTPS DNS resource records necessary for ECH.
val client = OkHttpClient.Builder()
  .dns(AndroidDns())
  .build()

• New: OkHttp artifacts are now signed with our [new signing key]. This project and three sibling projects ([Retrofit], [Okio], and [SQLDelight]) recently joined [the Commonhaus Foundation].
• Fix: MockWebServer’s @StartStop annotation now supports @Nested JUnit 5 tests.
• Fix: Our default TLS hostname verifier now reject hosts that fail IP canonicalization.
• Fix: Closing a multipart part's sink no longer closes the entire request body.
• Fix: Flush HTTP/1 request bodies before detaching the timeout. We had a bug where timeouts

... (truncated)

• a94bdf1 Prepare for release 5.5.0.
• ecc3b05 Use a fixed size for DoH request body (#9687)
• 9926082 Revert "Use a fixed size for DoH request body" (#9686)
• 0070c2e Use a fixed size for DoH request body
• 1576453 Order ServiceMetadata records per the spec (#9683)
• fb582e9 Flip wiring of Dns.SYSTEM (#9682)
• 4e884ab retryOnConnectionFailure doesn't impact ECH retries (#9681)
• 0433cee Only one contributing.md doc (#9678)
• a2cf5aa Don't recover after an ECH public_name fails to verify (#9680)
• 5410de9 Test ECH + HTTP proxy (#9671)
• Additional commits viewable in compare view