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OkHttp 4.x Change Log

Version 4.10.0


  • Upgrade: Kotlin 1.6.20.
  • Upgrade: Okio 3.0.0.
  • Fix: Recover gracefully when Android’s NativeCrypto crashes with "ssl == null". This occurs when OkHttp retrieves ALPN state on a closed connection.

Version 4.9.3


  • Fix: Don’t fail HTTP/2 responses if they complete before a RST_STREAM is sent.

Version 4.9.2


  • Fix: Don’t include potentially-sensitive header values in Headers.toString() or exceptions. This applies to Authorization, Cookie, Proxy-Authorization, and Set-Cookie headers.
  • Fix: Don’t crash with an InaccessibleObjectException when running on JDK17+ with strong encapsulation enabled.
  • Fix: Strictly verify hostnames used with OkHttp’s HostnameVerifier. Programs that make direct manual calls to HostnameVerifier could be defeated if the hostnames they pass in are not strictly ASCII. This issue is tracked as CVE-2021-0341.

Version 4.9.1


  • Fix: Work around a crash in Android 10 and 11 that may be triggered when two threads concurrently close an SSL socket. This would have appeared in crash logs as NullPointerException: bio == null.

Version 4.9.0


With this release, okhttp-tls no longer depends on Bouncy Castle and doesn’t install the Bouncy Castle security provider. If you still need it, you can do it yourself:


You will also need to configure this dependency:

dependencies {
  implementation "org.bouncycastle:bcprov-jdk15on:1.65"

Version 4.8.1


  • Fix: Don’t crash in HeldCertificate.Builder when creating certificates on older versions of Android, including Android 6. We were using a feature of SimpleDateFormat that wasn’t available in those versions!

Version 4.8.0


  • New: Change HeldCertificate.Builder to use its own ASN.1 certificate encoder. This is part of our effort to remove the okhttp-tls module’s dependency on Bouncy Castle. We think Bouncy Castle is great! But it’s a large dependency (6.5 MiB) and its security provider feature impacts VM-wide behavior.

  • New: Reduce contention for applications that make a very high number of concurrent requests. Previously OkHttp used its connection pool as a lock when making changes to connections and calls. With this change each connection is locked independently.

  • Upgrade: Okio 2.7.0.

  • Fix: Avoid log messages like “Didn’t find class org.conscrypt.ConscryptHostnameVerifier” when detecting the TLS capabilities of the host platform.

  • Fix: Don’t crash in HttpUrl.topPrivateDomain() when the hostname is malformed.

  • Fix: Don’t attempt Brotli decompression if the response body is empty.

Version 4.7.2


  • Fix: Don’t crash inspecting whether the host platform is JVM or Android. With 4.7.0 and 4.7.1 we had a crash IllegalArgumentException: Not a Conscrypt trust manager because we depended on initialization order of companion objects.

Version 4.7.1


  • Fix: Pass the right arguments in the trust manager created for addInsecureHost(). Without the fix insecure hosts crash with an IllegalArgumentException on Android.

Version 4.7.0


  • New: HandshakeCertificates.Builder.addInsecureHost() makes it easy to turn off security in private development environments that only carry test data. Prefer this over creating an all-trusting TrustManager because only hosts on the allowlist are insecure. From our DevServer sample:

    val clientCertificates = HandshakeCertificates.Builder()
    val client = OkHttpClient.Builder()
        .sslSocketFactory(clientCertificates.sslSocketFactory(), clientCertificates.trustManager)
  • New: Add cacheHit, cacheMiss, and cacheConditionalHit() events to EventListener. Use these in logs, metrics, and even test cases to confirm your cache headers are configured as expected.

  • New: Constant string okhttp3.VERSION. This is a string like “4.5.0-RC1”, “4.5.0”, or “4.6.0-SNAPSHOT” indicating the version of OkHttp in the current runtime. Use this to include the OkHttp version in custom User-Agent headers.

  • Fix: Don’t crash when running as a plugin in Android Studio Canary 4.1. To enable platform-specific TLS features OkHttp must detect whether it’s running in a JVM or in Android. The upcoming Android Studio runs in a JVM but has classes from Android and that confused OkHttp!

  • Fix: Include the header Accept: text/event-stream for SSE calls. This header is not added if the request already contains an Accept header.

  • Fix: Don’t crash with a NullPointerException if a server sends a close while we’re sending a ping. OkHttp had a race condition bug.

Version 4.6.0


  • Fix: Follow HTTP 307 and 308 redirects on methods other than GET and POST. We’re reluctant to change OkHttp’s behavior in handling common HTTP status codes, but this fix is overdue! The new behavior is now consistent with RFC 7231, which is newer than OkHttp itself. If you want this update with the old behavior use this interceptor.

  • Fix: Don’t crash decompressing web sockets messages. We had a bug where we assumed deflated bytes in would always yield deflated bytes out and this isn’t always the case!

  • Fix: Reliably update and invalidate the disk cache on windows. As originally designed our internal DiskLruCache assumes an inode-like file system, where it’s fine to delete files that are currently being read or written. On Windows the file system forbids this so we must be more careful when deleting and renaming files.

  • Fix: Don’t crash on Java 8u252 which introduces an API previously found only on Java 9 and above. See Jetty’s overview of the API change and its consequences.

  • New: MultipartReader is a streaming decoder for MIME multipart (RFC 2045) messages. It complements MultipartBody which is our streaming encoder.

    val response: Response = call.execute()
    val multipartReader = MultipartReader(response.body!!)
    multipartReader.use {
      while (true) {
        val part = multipartReader.nextPart() ?: break
        process(part.headers, part.body)
  • New: MediaType.parameter() gets a parameter like boundary from a media type like multipart/mixed; boundary="abc".

  • New: Authenticator.JAVA_NET_AUTHENTICATOR forwards authentication requests to This obsoletes JavaNetAuthenticator in the okhttp-urlconnection module.

  • New: CertificatePinner now offers an API for inspecting the configured pins.

  • Upgrade: Okio 2.6.0.

  • Upgrade: data. This powers HttpUrl.topPrivateDomain(). It’s also how OkHttp knows which domains can share cookies with one another.

  • Upgrade: Bouncy Castle 1.65. This dependency is required by the okhttp-tls module.

  • Upgrade: Kotlin 1.3.71.

Version 4.5.0


This release fixes a severe bug where OkHttp incorrectly detected and recovered from unhealthy connections. Stale or canceled connections were incorrectly attempted when they shouldn’t have been, leading to rare cases of infinite retries. Please upgrade to this release!

  • Fix: don’t return stale DNS entries in DnsOverHttps. We were caching DNS results indefinitely rather than the duration specified in the response’s cache-control header.
  • Fix: Verify certificate IP addresses in canonical form. When a server presents a TLS certificate containing an IP address we must match that address against the URL’s IP address, even when the two addresses are encoded differently, such as and 0::0:0:FFFF:C0A8:101. Note that OkHttp incorrectly rejected valid certificates resulting in a failure to connect; at no point were invalid certificates accepted.
  • New: OkHttpClient.Builder.minWebSocketMessageToCompress() configures a threshold for compressing outbound web socket messages. Configure this with 0L to always compress outbound messages and Long.MAX_VALUE to never compress outbound messages. The default is 1024L which compresses messages of size 1 KiB and larger. (Inbound messages are compressed or not based on the web socket server’s configuration.)
  • New: Defer constructing Inflater and Deflater instances until they are needed. This saves memory if web socket compression is negotiated but not used.

Version 4.5.0-RC1


This release candidate turns on web socket compression.

The spec includes a sophisticated mechanism for client and server to negotiate compression features. We strive to offer great performance in our default configuration and so we’re making compression the default for everyone starting with this release candidate.

Please be considerate of your servers and their operators as you roll out this release. Compression saves bandwidth but it costs CPU and memory! If you run into a problem you may need to adjust or disable the permessage-deflate compression settings on your server.

Note that OkHttp won’t use compression when sending messages smaller than 1 KiB.

  • Fix: Don’t crash when the URL hostname contains an underscore on Android.
  • Fix: Change HTTP/2 to use a daemon thread for its socket reader. If you’ve ever seen a command line application hang after all of the work is done, it may be due to a non-daemon thread like this one.
  • New: Include suppressed exceptions when all routes to a target service fail.

Version 4.4.1


  • Fix: Don’t reuse a connection on redirect if certs match but DNS does not. For better locality and performance OkHttp attempts to use the same pooled connection across redirects and follow-ups. It independently shares connections when the IP addresses and certificates match, even if the host names do not. In 4.4.0 we introduced a regression where we shared a connection when certificates matched but the DNS addresses did not. This would only occur when following a redirect from one hostname to another, and where both hosts had common certificates.

  • Fix: Don’t fail on a redirect when a client has configured a ‘trust everything’ trust manager. Typically this would cause certain redirects to fail in debug and development configurations.

Version 4.4.0


  • New: Support canceled() as an event that can be observed by EventListener. This should be useful for splitting out canceled calls in metrics.

  • New: Publish a bill of materials (BOM) for OkHttp. Depend on this from Gradle or Maven to keep all of your OkHttp artifacts on the same version, even if they’re declared via transitive dependencies. You can even omit versions when declaring other OkHttp dependencies.

    dependencies {
       api("com.squareup.okhttp3:okhttp")              // No version!
       api("com.squareup.okhttp3:logging-interceptor") // No version!
  • New: Upgrade to Okio 2.4.3.

  • Fix: Limit retry attempts for HTTP/2 REFUSED_STREAM and CANCEL failures.

  • Fix: Retry automatically when incorrectly sharing a connection among multiple hostnames. OkHttp shares connections when hosts share both IP addresses and certificates, such as and If a server refuses such sharing it will return HTTP 421 and OkHttp will automatically retry on an unshared connection.
  • Fix: Don’t crash if a TLS tunnel’s response body is truncated.
  • Fix: Don’t track unusable routes beyond their usefulness. We had a bug where we could track certain bad routes indefinitely; now we only track the ones that could be necessary.
  • Fix: Defer proxy selection until a proxy is required. This saves calls to ProxySelector on calls that use a pooled connection.

Version 4.3.1


  • Fix: Don’t crash with a NullPointerException when a web socket is closed before it connects. This regression was introduced in OkHttp 4.3.0.
  • Fix: Don’t crash with an IllegalArgumentException when using custom trust managers on Android 10. Android uses reflection to look up a magic checkServerTrusted() method and we didn’t have it.
  • Fix: Explicitly specify the remote server name when making HTTPS connections on Android 5. In 4.3.0 we introduced a regression where server name indication (SNI) was broken on Android 5.

Version 4.3.0


  • Fix: Degrade HTTP/2 connections after a timeout. When an HTTP/2 stream times out it may impact the stream only or the entire connection. With this fix OkHttp will now send HTTP/2 pings after a stream timeout to determine whether the connection should remain eligible for pooling.

  • Fix: Don’t call EventListener.responseHeadersStart() or responseBodyStart() until bytes have been received. Previously these events were incorrectly sent too early, when OkHttp was ready to read the response headers or body, which mislead tracing tools. Note that the responseFailed() event always used to follow one of these events; now it may be sent without them.

  • New: Upgrade to Kotlin 1.3.61.

  • New: Match any number of subdomains with two asterisks in CertificatePinner. For example, ** matches, and

  • New: Share threads more aggressively between OkHttp’s HTTP/2 connections, connection pool, web sockets, and cache. OkHttp has a new internal task runner abstraction for managed task scheduling. In your debugger you will see new thread names and more use of daemon threads.

  • Fix: Don’t drop callbacks on unexpected exceptions. When an interceptor throws an unchecked exception the callback is now notified that the call was canceled. The exception is still sent to the uncaught exception handler for reporting and recovery.

  • Fix: Un-deprecate MockResponse.setHeaders() and other setters. These were deprecated in OkHttp 4.0 but that broke method chaining for Java callers.

  • Fix: Don’t crash on HTTP/2 HEAD requests when the Content-Length header is present but is not consistent with the length of the response body.

  • Fix: Don’t crash when converting a HttpUrl instance with an unresolvable hostname to a URI. The new behavior strips invalid characters like " and { from the hostname before converting.

  • Fix: Undo a performance regression introduced in OkHttp 4.0 caused by differences in behavior between Kotlin’s assert() and Java’s assert(). (Kotlin always evaluates the argument; Java only does when assertions are enabled.)

  • Fix: Honor RequestBody.isOneShot() in HttpLoggingInterceptor.

Version 4.2.2


  • Fix: When closing a canceled HTTP/2 stream, don’t send the END_STREAM flag. This could cause the server to incorrectly interpret the stream as having completed normally. This is most useful when a request body needs to cancel its own call.

Version 4.2.1


  • Fix: In 4.1.0 we introduced a performance regression that prevented connections from being pooled in certain situations. We have good test coverage for connection pooling but we missed this because it only occurs if you have proxy configured and you share a connection pool among multiple OkHttpClient instances.

    This particularly-subtle bug was caused by us assigning each OkHttpClient instance its own NullProxySelector when an explicit proxy is configured. But we don’t share connections when the proxy selectors are different. Ugh!

Version 4.2.0


  • New: API to decode a certificate and private key to create a HeldCertificate. This accepts a string containing both a certificate and PKCS #8-encoded private key.

    val heldCertificate = HeldCertificate.decode("""
        |-----BEGIN CERTIFICATE-----
        |-----END CERTIFICATE-----
        |-----BEGIN PRIVATE KEY-----
        |-----END PRIVATE KEY-----
    val handshakeCertificates = HandshakeCertificates.Builder()
    val server = MockWebServer()
    server.useHttps(handshakeCertificates.sslSocketFactory(), false)

    Get these strings with HeldCertificate.certificatePem() and privateKeyPkcs8Pem().

  • Fix: Handshake now returns peer certificates in canonical order: each certificate is signed by the certificate that follows and the last certificate is signed by a trusted root.

  • Fix: Don’t lose HTTP/2 flow control bytes when incoming data races with a stream close. If this happened enough then eventually the connection would stall.

  • Fix: Acknowledge and apply inbound HTTP/2 settings atomically. Previously we had a race where we could use new flow control capacity before acknowledging it, causing strict HTTP/2 servers to fail the call.

Version 4.1.1


  • Fix: Don’t drop repeated headers when validating cached responses. In our Kotlin upgrade we introduced a regression where we iterated the number of unique header names rather than then number of unique headers. If you’re using OkHttp’s response cache this may impact you.

Version 4.1.0


  • OkHttp’s new okhttp-brotli module implements Brotli compression. Install the interceptor to enable Brotli compression, which compresses 5-20% smaller than gzip.

    val client = OkHttpClient.Builder()

    This artifact has a dependency on Google’s Brotli decoder (95 KiB).

  • New: EventListener.proxySelectStart(), proxySelectEnd() events give visibility into the proxy selection process.

  • New: Response.byteString() reads the entire response into memory as a byte string.
  • New: OkHttpClient.x509TrustManager accessor.
  • New: Permit new WebSocket response codes: 1012 (Service Restart), 1013 (Try Again Later), and 1014 (invalid response from the upstream).
  • New: Build with Kotlin 1.3.41, BouncyCastle 1.62, and Conscrypt 2.2.1.
  • Fix: Recover gracefully when a coalesced connection immediately goes unhealthy.
  • Fix: Defer the SecurityException when looking up the default proxy selector.
  • Fix: Don’t use brackets formatting IPv6 host names in MockWebServer.
  • Fix: Don’t permit cache iterators to remove entries that are being written.

Version 4.0.1


  • Fix: Tolerate null-hostile lists in public API. Lists created with List.of(...) don’t like it when you call contains(null) on them!
  • Fix: Retain binary-compatibility in okhttp3.internal.HttpHeaders.hasBody(). Some unscrupulous coders call this and we don’t want their users to suffer.

Version 4.0.0


This release upgrades OkHttp to Kotlin. We tried our best to make fast and safe to upgrade from OkHttp 3.x. We wrote an upgrade guide to help with the migration and a blog post to explain it.

  • Fix: Target Java 8 bytecode for Java and Kotlin.

Version 4.0.0-RC3


  • Fix: Retain binary-compatibility in okhttp3.internal.HttpMethod. Naughty third party SDKs import this and we want to ease upgrades for their users.

Version 4.0.0-RC2


  • New: Require Kotlin 1.3.40.
  • New: Change the Kotlin API from File.toRequestBody() to File.asRequestBody() and BufferedSource.toResponseBody() to BufferedSource.asResponseBody(). If the returned value is a view of what created it, we use as.
  • Fix: Permit response codes of zero for compatibility with OkHttp 3.x.
  • Fix: Change the return type of MockWebServer.takeRequest() to be nullable.
  • Fix: Make Call.clone() public to Kotlin callers.

Version 4.0.0-RC1


  • First stable preview of OkHttp 4.

Version 3.x

Change log