Retrofit, which has always been loved by Android and Java/Kotlin developers, finally released a major update, version 3.0, on May 15, 2025. Many developers are already using it as an essential network library, but there are also many developers who haven't tried Retrofit yet or are considering upgrading to the latest version.

In this article, we've summarized the basic features and benefits of Retrofit, as well as the major changes and significance of Retrofit 3.0.

What is Retrofit?

Retrofit helps you easily implement HTTP API communication in Android and Java/Kotlin environments network libraryThis is it. Internally, OkHttp is used to provide stable and fast network processing performance.

The biggest advantage Declarative API designIt increases development productivity by replacing complex request logic with simple interface definitions.

Key features

1. declarative interface

Previously, processing an HTTP request required the following lengthy code:

However, with Retrofit, requests can be defined with a simple interface, as shown below.

2. Flexible data transformation

Various conversion libraries such as Gson, Jackson, and Moshi can be easily integrated.

3. OkHttp-based stability

Retrofit provides fast and reliable network communication by delegating part of the network processing to OkHttp. OkHttp's powerful caching mechanism and interceptor functions can be used to efficiently handle various network demands.

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Retrofit's market position

Retrofit is already widely used in numerous apps. According to market statistics:

• Of all Android apps about 17%It uses Retrofit
• What percentage of apps use Retrofit in the top popular apps drug 36%
• The cumulative number of downloads for apps using Retrofit More than 200 billion times

Retrofit is also increasingly being used in server environments beyond mobile. Retrofit is increasingly being adopted as an HTTP client in microservices architectures or Spring Boot-based backend services. these scalability Thanks to this, Retrofit continues to be loved in diverse development environments without platform restrictions.

The relationship between Retrofit and OkHttp

Retrofit internally uses OkHttp to process network requests and responses. While Retrofit is responsible for designing the API and defining requests, OkHttp is responsible for sending actual network requests and receiving responses.

Thanks to this combination, Retrofit High performanceet stabilityIt provides, and you can also take advantage of OkHttp's powerful features (such as interceptors, caching, and connection pooling) as is.

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Retrofit 3.0 released!

Compared to previous versions, Retrofit 3.0 Kotlin-centered design, Improved asynchronous processing, OkHttp upgrade We have greatly improved the developer experience in various aspects such as

Key changes in Retrofit 3.0

1. A complete Kotlin-centric transition

Until now, Retrofit was Java-based, but starting with 3.0, the internal structure was Completely Kotlin-basedIt has been rewritten as As the number of apps using Kotlin increases, it provides a more familiar interface and functionality for Kotlin developers.

Example (Kotlin Null Safety):

With Kotlin-based design Null stabilityThis has been enhanced, and it is possible to write more concise code.

2. Instead of Call Suspend funStreamlined asynchronous processing through

The existing Call interface is for asynchronous processing enqueue I had to use callbacks Starting with Retrofit 3.0, Kotlin coroutine's Suspend funAsynchronous code has been made much simpler with support for

Traditional method:

A new approach:

Suspend fun The introduction made complex asynchronous processing code simpler and more intuitive.

Retrofit 3.0's Kotlin transition, why is it important?

The biggest change in Retrofit 3.0, the Kotlin-centered design, goes beyond a simple language switch. Kotlin has spread rapidly since it was adopted as the official language for Android. Modern programming paradigm, high readability, increased productivity It has many advantages, etc.

As Retrofit is restructured around Kotlin, developers can write simpler and safer code and enjoy an environment optimized for modern application development flows. Build a modern Kotlin-based development environment with Retrofit 3.0 and experience more stable and efficient application development.