# What Are the Dependencies of Abseil C++? Essential Build Requirements Explained

> Discover Abseil C++ dependencies. Learn essential build requirements like CMake and C++17 compiler. See optional GoogleTest needs for testing.

- Repository: [Abseil/abseil-cpp](https://github.com/abseil/abseil-cpp)
- Tags: deep-dive
- Published: 2026-07-19

---

**Abseil C++ requires only CMake 3.16 or newer, a C++17-compliant compiler, and the system's thread library to build; optional testing features depend solely on GoogleTest.**

Abseil C++ is a header-only (with optional compiled parts) collection of utilities from Google that builds on the C++17 language standard. When integrating the `abseil/abseil-cpp` repository into your project, understanding its minimal dependency footprint ensures you link no unnecessary third-party runtime libraries. The following guide breaks down every build requirement as declared in the source code.

## Core Build Dependencies

### CMake 3.16 or Newer

The Abseil C++ library uses CMake as its primary build system generator. In the top-level [`CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/CMakeLists.txt), the project declares a minimum required version of 3.16 to access modern CMake features such as `cxx_std_17`.

```cmake
cmake_minimum_required(VERSION 3.16)

```

*According to the source code at line 19 of [`CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/CMakeLists.txt), this version requirement is mandatory.*

### C++17 Standard Library

All Abseil code is written for C++17, with some components optionally utilizing C++20 features. The build system enforces this via the `ABSL_PROPAGATE_CXX_STD` option defined in [`CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/CMakeLists.txt) (lines 48-50), which ensures the C++ standard propagates correctly to dependent targets.

### System Thread Library

Abseil's synchronization primitives—including `absl::Mutex` and `absl::ConditionVariable`—require threading support. In [`CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/CMakeLists.txt) (lines 96-99), the build system explicitly searches for and requires the platform's thread library:

```cmake
find_package(Threads REQUIRED)

```

On Unix systems, this typically resolves to **POSIX `pthread`**, while Windows targets use native Windows threads.

## Optional Dependencies

### GoogleTest for Development and Testing

GoogleTest is only required when building Abseil's own test suite or the test-helper libraries. This dependency is controlled via the `ABSL_BUILD_TESTING` and `ABSL_BUILD_TEST_HELPERS` CMake options. When enabled, [`CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/CMakeLists.txt) (lines 137-140) invokes:

```cmake
find_package(GTest REQUIRED)

```

The repository includes `CMake/Googletest/DownloadGTest.cmake` to automatically fetch GoogleTest when `ABSL_USE_EXTERNAL_GOOGLETEST` is set to `OFF`.

## Build System Configuration

### Configuring Abseil with CMake

When integrating Abseil as a subdirectory, the [`CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/CMakeLists.txt) automatically handles the thread dependency resolution.

```cmake

# CMakeLists.txt

cmake_minimum_required(VERSION 3.16)
project(my_app LANGUAGES CXX)

# Pull in Abseil (assumes the repository is a subdirectory)

add_subdirectory(abseil-cpp)

add_executable(my_app main.cc)
target_link_libraries(my_app PRIVATE absl::base absl::strings absl::time)

```

*The `add_subdirectory(abseil-cpp)` call triggers the logic in [`abseil-cpp/CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/abseil-cpp/CMakeLists.txt) which automatically pulls in the `Threads` dependency.*

### Configuring Abseil with Bazel

**Bazel** is the alternative, officially-supported build system. Dependencies are managed internally by Bazel's repository rules defined in `BUILD.bazel`.

```python

# BUILD

cc_binary(
    name = "my_app",
    srcs = ["main.cc"],
    deps = [
        "@abseil//absl/base",
        "@abseil//absl/strings",
        "@abseil//absl/time",
    ],
)

```

*Bazel fetches the Abseil repository as an external dependency (`@abseil`).*

### Enabling Test Helpers

To build with the optional testing utilities:

```cmake

# Enable testing and import GoogleTest

set(ABSL_BUILD_TESTING ON)
set(ABSL_BUILD_TEST_HELPERS ON)
set(ABSL_USE_EXTERNAL_GOOGLETEST OFF)   # let Abseil download GTest

add_subdirectory(abseil-cpp)

# Build a test that uses the helper library

add_executable(my_test test.cc)
target_link_libraries(my_test PRIVATE absl::test_helper GTest::gtest_main)

```

*When `ABSL_BUILD_TEST_HELPERS` is ON, the script in `CMake/Googletest/DownloadGTest.cmake` handles the GoogleTest acquisition.*

## Summary

- **Abseil C++** maintains a minimal dependency footprint, requiring only standard tooling.
- **CMake 3.16+**, a **C++17 compiler**, and the **system thread library** are mandatory for all builds.
- **GoogleTest** is only required when building tests or test helpers, and can be downloaded automatically.
- **Bazel** users rely on the `BUILD.bazel` rules rather than CMake for dependency management.
- No third-party runtime libraries are linked unless you explicitly enable optional testing facilities.

## Frequently Asked Questions

### Does Abseil C++ require Boost?

No. Abseil C++ is designed to depend exclusively on the C++ standard library and the system thread library. It does not link against Boost or any other third-party runtime libraries unless you explicitly enable optional testing features.

### Is threading support mandatory for Abseil C++?

Yes. The `find_package(Threads REQUIRED)` directive in [`CMakeLists.txt`](https://github.com/abseil/abseil-cpp/blob/main/CMakeLists.txt) makes threading support mandatory. Core components like `absl::Mutex` and `absl::ConditionVariable` require the system thread library (POSIX `pthread` on Unix, native Windows threads on Windows).

### How do I enable testing dependencies in Abseil C++?

Set the CMake options `ABSL_BUILD_TESTING=ON` and `ABSL_BUILD_TEST_HELPERS=ON`. If `ABSL_USE_EXTERNAL_GOOGLETEST` is `OFF`, Abseil will use `CMake/Googletest/DownloadGTest.cmake` to automatically fetch GoogleTest. If set to `ON`, you must provide an external GoogleTest installation.

### What is the minimum C++ standard required for Abseil C++?

Abseil requires **C++17** at minimum. While specific compiler version minimums vary by platform, any compiler fully supporting the C++17 standard will work. Some optional features may utilize C++20 if available.