This section highlights **venture-backed** and **company-supported** solutions from companies that sponsor FastAPI. These products provide **additional features** and **integrations** on top of high-quality generated SDKs.

By ✨ [**sponsoring FastAPI**](../help-fastapi.md#sponsor-the-author){.internal-link target=_blank} ✨, these companies help ensure the framework and its **ecosystem** remain healthy and **sustainable**.

Django REST framework was created to be a flexible toolkit for building Web APIs using Django underneath, to improve its API capabilities.

It is used by many companies including Mozilla, Red Hat and Eventbrite.

It was one of the first examples of **automatic API documentation**, and this was specifically one of the first ideas that inspired "the search for" **FastAPI**.

/// note

public abstract interface class okhttp3/Dns {
	public static final field Companion Lokhttp3/Dns$Companion;
	public static final field SYSTEM Lokhttp3/Dns;
	public abstract fun lookup (Ljava/lang/String;)Ljava/util/List;
}

public final class okhttp3/Dns$Companion {
}

public abstract class okhttp3/EventListener {
	public static final field Companion Lokhttp3/EventListener$Companion;
	public static final field NONE Lokhttp3/EventListener;

public abstract interface class okhttp3/Dns {
	public static final field Companion Lokhttp3/Dns$Companion;
	public static final field SYSTEM Lokhttp3/Dns;
	public abstract fun lookup (Ljava/lang/String;)Ljava/util/List;
}

public final class okhttp3/Dns$Companion {
}

public abstract class okhttp3/EventListener {
	public static final field Companion Lokhttp3/EventListener$Companion;
	public static final field NONE Lokhttp3/EventListener;

	public static final field Companion Lokhttp3/logging/HttpLoggingInterceptor$Logger$Companion;
	public static final field DEFAULT Lokhttp3/logging/HttpLoggingInterceptor$Logger;
	public abstract fun log (Ljava/lang/String;)V
}

public final class okhttp3/logging/HttpLoggingInterceptor$Logger$Companion {
}

public final class okhttp3/logging/LoggingEventListener : okhttp3/EventListener {

  fun sha256(): ByteString {
    val hashingSink = HashingSink.sha256(blackholeSink())
    hashingSink.buffer().use {
      this.writeTo(it)
    }
    return hashingSink.hash
  }

  companion object {
    /** Empty request body with no content-type. */
    @JvmField
    val EMPTY: RequestBody = ByteString.EMPTY.toRequestBody()

    /**

import kotlin.time.Duration
import kotlin.time.Duration.Companion.milliseconds
import kotlin.time.measureTime
import mockwebserver3.MockResponse
import mockwebserver3.MockWebServer
import mockwebserver3.SocketEffect.CloseSocket
import mockwebserver3.SocketEffect.ShutdownConnection
import mockwebserver3.junit5.StartStop
import okhttp3.Headers.Companion.headersOf
import okhttp3.HttpUrl.Companion.toHttpUrl

import java.io.FileInputStream
import java.io.IOException
import java.nio.file.Path
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.RequestBody.Companion.asRequestBody
import okhttp3.RequestBody.Companion.toRequestBody
import okio.Buffer
import okio.FileSystem
import okio.Path.Companion.toOkioPath
import org.junit.jupiter.api.Assertions.assertThrows
import org.junit.jupiter.api.BeforeEach

import kotlin.reflect.KClass
import okhttp3.Handshake.Companion.handshake
import okhttp3.Headers.Companion.headersOf
import okhttp3.Headers.Companion.toHeaders
import okhttp3.HttpUrl.Companion.toHttpUrl
import okhttp3.HttpUrl.Companion.toHttpUrlOrNull
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.MediaType.Companion.toMediaTypeOrNull
import okhttp3.RequestBody.Companion.asRequestBody

import okhttp3.internal.platform.Platform
import okhttp3.internal.platform.Platform.Companion.WARN
import okhttp3.internal.toLongOrDefault
import okio.Buffer
import okio.BufferedSink
import okio.BufferedSource
import okio.ByteString.Companion.decodeBase64
import okio.ByteString.Companion.encodeUtf8
import okio.ByteString.Companion.toByteString
import okio.FileSystem
import okio.ForwardingSink
import okio.ForwardingSource