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Bazel vs Webpack: What are the differences?

Key Differences between Bazel and Webpack

Bazel and Webpack are both build tools for compiling and bundling code, but they have different approaches and functionalities. Here are the key differences between Bazel and Webpack:

  1. Build System: Bazel is a multi-language build system developed by Google, primarily designed for large-scale projects. It provides a distributed caching mechanism and incremental builds, allowing for fast and efficient build times. On the other hand, Webpack is a module bundler that is mainly used in the JavaScript ecosystem for bundling and optimizing web applications. It focuses on providing a highly customizable and flexible build configuration.

  2. Supported Languages: Bazel supports multiple programming languages such as Java, C++, Python, TypeScript, and more. It enables the creation of monorepos where different languages can coexist and be built together. Webpack, on the other hand, focuses on JavaScript and its ecosystem, including frameworks like React and Vue. It provides loaders and plugins to preprocess and bundle various types of assets such as CSS, images, and fonts.

  3. Dependency Management: Bazel uses a dependency graph to manage dependencies between different targets and provides strict build isolation. It ensures that only the necessary parts of the code are rebuilt when changes occur, resulting in faster build times. Webpack, on the other hand, uses a dependency graph to resolve and bundle JavaScript modules, allowing for efficient code splitting and lazy loading.

  4. Build Performance: Bazel's distributed caching mechanism and incremental builds make it highly performant, especially in large projects where only a small portion of the code changes between builds. It avoids building already built or unchanged code, significantly reducing build times. Webpack also offers optimizations like code splitting and caching, but its performance may degrade in larger projects with frequent changes due to the need to rebuild the entire bundle.

  5. Community and Ecosystem: Bazel has been mainly adopted by large organizations and projects with complex needs, and it has a smaller community compared to Webpack. Webpack, being widely used in the JavaScript ecosystem, has a larger and more active community. This results in a broader range of plugins, loaders, and community-contributed configurations, making it easier to set up and customize builds for different use cases.

  6. Configurability: Bazel has a declarative configuration approach. Build rules are defined in a language-agnostic way using a BUILD file, allowing for clear and reproducible builds. Webpack, on the other hand, provides a flexible and highly configurable JavaScript API for setting up the build configuration. It allows developers to customize various aspects of the build process, such as loaders, plugins, and optimizations, using JavaScript code.

In summary, Bazel is a powerful and efficient build system designed for large-scale projects with multi-language support and strict build isolation. Webpack, on the other hand, is primarily focused on JavaScript and provides a flexible and customizable module bundling solution for web applications. The choice between Bazel and Webpack depends on the specific needs of the project, the size and complexity of the codebase, and the desired level of configurability.

Decisions about Bazel and Webpack
Aleksandr Filatov
Contract Software Engineer - Microsoft · | 4 upvotes · 286K views
Why migrated?

I could define the next points why we have to migrate:

  • Decrease build time of our application. (It was the main cause).
  • Also jspm install takes much more time than npm install.
  • Many config files for SystemJS and JSPM. For Webpack you can use just one main config file, and you can use some separate config files for specific builds using inheritance and merge them.
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We mostly use rollup to publish package onto NPM. For most all other use cases, we use the Meteor build tool (probably 99% of the time) for publishing packages. If you're using Node on FHIR you probably won't need to know rollup, unless you are somehow working on helping us publish front end user interface components using FHIR. That being said, we have been migrating away from Atmosphere package manager towards NPM. As we continue to migrate away, we may publish other NPM packages using rollup.

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Pros of Bazel
Pros of Webpack
  • 28
  • 20
    Deterministic incremental builds
  • 17
  • 16
  • 14
    Enforces declared inputs/outputs
  • 10
    High-level build language
  • 9
  • 5
    Multi-platform support
  • 5
  • 4
    Dependency management
  • 2
    Windows Support
  • 2
  • 1
    Android Studio integration
  • 309
    Most powerful bundler
  • 182
    Built-in dev server with livereload
  • 142
    Can handle all types of assets
  • 87
    Easy configuration
  • 22
  • 4
    Overengineered, Underdeveloped
  • 2
    Makes it easy to bundle static assets
  • 2
  • 1
  • 1
    Better support in Browser Dev-Tools

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Cons of Bazel
Cons of Webpack
  • 3
    No Windows Support
  • 2
    Bad IntelliJ support
  • 1
    Poor windows support for some languages
  • 1
    Constant breaking changes
  • 1
    Learning Curve
  • 1
    Lack of Documentation
  • 15
    Hard to configure
  • 5
    No clear direction
  • 2
    Spaghetti-Code out of the box
  • 2
    SystemJS integration is quite lackluster
  • 2
    Loader architecture is quite a mess (unreliable/buggy)
  • 2
    Fire and Forget mentality of Core-Developers

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What is Bazel?

Bazel is a build tool that builds code quickly and reliably. It is used to build the majority of Google's software, and thus it has been designed to handle build problems present in Google's development environment.

What is Webpack?

A bundler for javascript and friends. Packs many modules into a few bundled assets. Code Splitting allows to load parts for the application on demand. Through "loaders" modules can be CommonJs, AMD, ES6 modules, CSS, Images, JSON, Coffeescript, LESS, ... and your custom stuff.

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What companies use Bazel?
What companies use Webpack?
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Mar 24 2021 at 12:57PM


What are some alternatives to Bazel and Webpack?
Pants is a build system for Java, Scala and Python. It works particularly well for a source code repository that contains many distinct projects.
Ansible is an IT automation tool. It can configure systems, deploy software, and orchestrate more advanced IT tasks such as continuous deployments or zero downtime rolling updates. Ansible’s goals are foremost those of simplicity and maximum ease of use.
Buck encourages the creation of small, reusable modules consisting of code and resources, and supports a variety of languages on many platforms.
It is used to control the software compilation process using simple platform and compiler independent configuration files, and generate native makefiles and workspaces that can be used in the compiler environment of the user's choice.
In a nutshell Jenkins CI is the leading open-source continuous integration server. Built with Java, it provides over 300 plugins to support building and testing virtually any project.
See all alternatives