Knapsack Pro

Netlify Build vs Circle CI comparison of Continuous Integration servers
What are the differences between Netlify Build and Circle CI?

Netlify Build

https://www.netlify.com/products/build/

Circle CI

https://circleci.com
Unique feature

Deploy your sites to global Netlify infrastructure

Every commit gets its own deployed version. Automatically attach a new Deploy Preview at a unique permanent URL whenever you submit a Pull/Merge Request. Set Netlify Build to deploy every branch in the repository for unlimited staging environments.

Premium Support

Type of product

SaaS

SaaS, Self-hosted / On Premise

Offers a free plan

Yes

300 build minutes/month, 1 concurrent CI build

Yes

Provides a free plan for it's SaaS solution, for up to 1000 build minutes per month, 1 container and 1 concurrent job. On top of this, it has a special Free Tier for open source projects, which extend the number of containers and concurrent jobs available.
Predictable pricing

Yes

Extra 500 build minutes costs $7/month. User seat $15/user/month.

Yes

Provides a calculator, based on the number of concurrent jobs and containers, which can be used to determine pricing before purchase. They also give a guideline based on the number of developers you employ (2-3 containers per full-time developer)
Support / SLA

Yes

99.99% uptime SLA for Starter and Pro plan. Business plan has negotiable SLA.

Yes

While it's community is not quite as vibrant as it is for Jenkins, CircleCI even offers support premium support for companies who cannot afford any downtime in their CI/CD pipelines (https://circleci.com/support/premium-support/). For the regular plans, all plans except the free tier offer official email support. The free tier only includes community support (Discuss, StackOverflow, etc.)
Paralellism
Every CI servers tends to address this differently (parallel, distributed, build matrix). Some of it is just marketing, and some is just nuance. For this table, parallel means that tasks can be run concurrently on the same machine, distributed means that tasks can be scaled horizontally, on multiple machines
How to split tests in parallel in the optimal way with Knapsack Pro

Yes

Starter plan (free) has only 1 concurrent build but Pro plan has 3 concurrent builds included.

Yes

CircleCI can run builds in parallel, each build in a completely isolated environment by using containers.
Distributed builds
distributed means that tasks can be scaled horizontally, on multiple machines
How to split tests in parallel in the optimal way with Knapsack Pro

Yes

High-Performance Builds - The premium build environment gives more concurrency, processing power and asynchronous deploys.

Yes

The SaaS version distributes builds by default, while the self-hosted version has all the tools built-in for managing the cluster of builder machines.
Containers support / Build environment

Yes

When you trigger a build on Netlify, their buildbot starts a Docker container to build your website. The buildbot will look for instructions about required languages and software needed to run your command before running build command. The instructions are called dependencies, and how you declare them depends on the programming languages and tools used in build. Build image selection is available. Until recently, all Netlify sites were built using the same build image. Netlify is experimenting with allowing customers to select from multiple Docker images with different operating systems and software versions.

Yes

CircleCI runs every build in a container, or VM, ensuring an isolated, local scope for each build. The environment is also reset with each build, which can highlight hard-to-track issues related to assumptions about the environment that the project is deployed to.
Analytics / Status overview
Analytics and overview referrs to the ability to, at a glance, see what's breaking (be it a certain task, or the build for a specific project)

Yes

Simple dashboard to see CI builds. Other than CI analytics Netlify has Netlify Analytics that brings data captured directly from their servers for your website.

Yes

Available by default in Circle CI: https://circleci.com/docs/2.0/status/#section=jobs. Aditionally, the Insights Dashboard provides a very useful overview on build times, error rates and status for your projects: https://circleci.com/docs/2.0/insights/#section=jobs
Management support
How easy is it to manage users / projects / assign roles and permissions and so on

Yes

Team members managment. Role-based access control only in business plan.

No (partial)

Using the Cloud plan for Circle CI requires no dedicated person for maintanence / management of the service. The CircleCI Server option (self-hosted) is also hassle free, as the process of installing and managing CircleCI and it's dependencies is automated. Developers are also given SSH acces to the builds (not the whole environment), while sys-admins can work on the host machine without worry about affecting the builds (which are containerized).
Self-hosted option

No

Yes

Hosted plans / SaaS

Yes

Yes

Build pipelines
A continuous delivery pipeline is a description of the process that the software goes through from a new code commit, through testing and other statical analysis steps all the way to the end-users of the product.

Yes, partially

Simple steps, define your own steps in bash commands

Yes

Pipelines in CircleCI are defined declaratively using an Yaml config file. CircleCI has special provisions for storing secrets in these files.
Reports
Reports are about the abilty to see specific reports (like code coverage or custom ones), but not necesarily tied in into a larger dashboard.

No

Yes

Reports are available
Ecosystem
Besides the official documentation and software, is there a large community using this product? Are there any community-driven tools / plugins that you can use?

No

There are only small helpful things like incoming webhooks so other services can trigger Netlify deploys, and send outgoing webhooks as a deploy starts, succeeds, or fails.

Yes, partially

While CircleCI doesn't natively support plugins, it's core features address all of the core functionality that a CI/CD service needs. For integrating with other platforms or tools, there are integrations such as https://slack.com/apps/A0F7VRE7N-circleci. Certain jobs are available as CircleCI Orbs: https://circleci.com/orbs/
Specific language support: Ruby
Some CI servers have built-in support for parsing RSpec or Istanbul output for example and we mention those. Some others make it even easier by detecting Gemfiles or package.json and automate parts of the process for the developer.

Yes

It has support for Ruby.

Yes

For collecting test metadata and coverage, there is built-in support for Ruby (specifically, Cucumber and RSpec). Setting this up takes very little time and is well-documented on CircleCI's docs.
Specific language support: JavaScript

Yes

It has support for JavaScript.

Yes

For collecting test metadata and coverage, there is built-in support for Javascript. For code coverage, CircleCI understands Istanbul output (Jest also uses Istanbul for the code coverage reports), while for test metadata, the JUnit output format is natively supported.
Integrations
1st party support for common tools (like Slack notifications, various VCS platforms, etc)

Yes

Netlify has incoming webhooks so other services can trigger Netlify deploys, and send outgoing webhooks as a deploy starts, succeeds, or fails. For instance you can integrate it with Slack.

Yes

Available as CircleCI Orbs: https://circleci.com/orbs/
API
Custom integreation is available, via an API or otherwise, it's mentioned separately as it allows further customization than any of the Ecosystem/Integration options

No

Yes

REST API documentation available at https://circleci.com/docs/api/#api-overview. Creating Orbs is also documented at https://circleci.com/docs/2.0/orb-author/#introduction
Auditing

N/A

N/A

Additional notes

How to get faster Circle CI builds with dynamic test suite split instead of deterministic split

How to split E2E tests on multiple CI nodes using Cypress.io test runner

Jest JavaScript Testing and CI parallelisation how to do it?

Circle CI parallelism integration

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