OkHttp
======

See the [project website][okhttp] for documentation and APIs.

HTTP is the way modern applications network. It’s how we exchange data & media. Doing HTTP
efficiently makes your stuff load faster and saves bandwidth.

OkHttp is an HTTP client that’s efficient by default:

 * HTTP/2 support allows all requests to the same host to share a socket.
 * Connection pooling reduces request latency (if HTTP/2 isn’t available).
 * Transparent GZIP shrinks download sizes.
 * Response caching avoids the network completely for repeat requests.

OkHttp perseveres when the network is troublesome: it will silently recover from common connection
problems. If your service has multiple IP addresses OkHttp will attempt alternate addresses if the
first connect fails. This is necessary for IPv4+IPv6 and services hosted in redundant data
centers. OkHttp supports modern TLS features (TLS 1.3, ALPN, certificate pinning). It can be
configured to fall back for broad connectivity.

Using OkHttp is easy. Its request/response API is designed with fluent builders and immutability. It
supports both synchronous blocking calls and async calls with callbacks.


Get a URL
---------

This program downloads a URL and prints its contents as a string. [Full source][get_example].

```java
OkHttpClient client = new OkHttpClient();

String run(String url) throws IOException {
  Request request = new Request.Builder()
      .url(url)
      .build();

  try (Response response = client.newCall(request).execute()) {
    return response.body().string();
  }
}
```


Post to a Server
----------------

This program posts data to a service. [Full source][post_example].

```java
public static final MediaType JSON
    = MediaType.get("application/json; charset=utf-8");

OkHttpClient client = new OkHttpClient();

String post(String url, String json) throws IOException {
  RequestBody body = RequestBody.create(json, JSON);
  Request request = new Request.Builder()
      .url(url)
      .post(body)
      .build();
  try (Response response = client.newCall(request).execute()) {
    return response.body().string();
  }
}
```

Further examples are on the [OkHttp Recipes page][recipes].


Requirements
------------

OkHttp works on Android 5.0+ (API level 21+) and on Java 8+.

OkHttp depends on [Okio][okio] for high-performance I/O and the [Kotlin standard library][kotlin]. Both are small libraries with strong backward-compatibility.

We highly recommend you keep OkHttp up-to-date. As with auto-updating web browsers, staying current
with HTTPS clients is an important defense against potential security problems. [We
track][tls_history] the dynamic TLS ecosystem and adjust OkHttp to improve connectivity and
security.

OkHttp uses your platform's built-in TLS implementation. On Java platforms OkHttp also supports
[Conscrypt][conscrypt], which integrates BoringSSL with Java. OkHttp will use Conscrypt if it is
the first security provider:

```java
Security.insertProviderAt(Conscrypt.newProvider(), 1);
```

The OkHttp 3.12.x branch supports Android 2.3+ (API level 9+) and Java 7+. These platforms lack
support for TLS 1.2 and should not be used. But because upgrading is difficult we will backport
critical fixes to the [3.12.x branch][okhttp_312x] through December 31, 2020.


Releases
--------

Our [change log][changelog] has release history.

The latest release is available on [Maven Central](https://search.maven.org/artifact/com.squareup.okhttp3/okhttp/4.4.1/jar).

```kotlin
implementation("com.squareup.okhttp3:okhttp:4.4.1")
```

Snapshot builds are [available][snap]. [R8 and ProGuard][r8_proguard] rules are available.


MockWebServer
-------------

OkHttp includes a library for testing HTTP, HTTPS, and HTTP/2 clients.

The latest release is available on [Maven Central](https://search.maven.org/artifact/com.squareup.okhttp3/mockwebserver/4.4.1/jar).

```kotlin
testImplementation("com.squareup.okhttp3:mockwebserver:4.4.1")
```

License
-------

```
Copyright 2019 Square, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
```

 [changelog]: http://square.github.io/okhttp/changelog/
 [conscrypt]: https://github.com/google/conscrypt/
 [get_example]: https://raw.github.com/square/okhttp/master/samples/guide/src/main/java/okhttp3/guide/GetExample.java
 [kotlin]: https://kotlinlang.org/
 [okhttp3_pro]: https://github.com/square/okhttp/blob/master/okhttp/src/main/resources/META-INF/proguard/okhttp3.pro
 [okhttp_312x]: https://github.com/square/okhttp/tree/okhttp_3.12.x
 [okhttp]: https://square.github.io/okhttp/
 [okio]: https://github.com/square/okio
 [post_example]: https://raw.github.com/square/okhttp/master/samples/guide/src/main/java/okhttp3/guide/PostExample.java
 [r8_proguard]: https://square.github.io/okhttp/r8_proguard/
 [recipes]: http://square.github.io/okhttp/recipes/
 [snap]: https://oss.sonatype.org/content/repositories/snapshots/
 [tls_history]: https://square.github.io/okhttp/tls_configuration_history/
