It’s been a while since I have checked what is going on in the development of CI/CD servers. I’ve worked extensively with Bamboo and TeamCity, and have a fair amount of exposure to GitLab and GitHub. Time for a quick survey.

I ran a quick web search to collect CI/CD servers that haven’t been on my radar yet. This resulted, together with the CI/CD servers I knew beforehand, in the following list of 14 servers. Some of them are CI/CD servers, some are only CI servers.

product	company	CI	CD	self-hosted	SaaS
AppVeyor	AppVeyor
Bamboo Data Center	Atlassian		x		x
BitBucket Pipelines	Atlassian		x	x
Buddy	BDY PSA			x
BuildKite	Buildkite			x
BuildMaster	Inedo				x
CloudBees CI	CloudBees		x	x
CircleCi	Circle Internet Services			x
Drone	Harness		x		x
GitLab	GitLab Inc.
GoCD	N/A
Semaphore	Semaphore Technologies
TeamCity	JetBrains		x
Travis CI	Idera

I do not include CI/CD servers of cloud providers like AWS CodePipeline + CodeBuild, Azure DevOps, or Google Cloud Build, but focus on solutions independent of any cloud providers. You won’t find GitHub Actions in the list, as I have zero interest in Microsoft products, and I would never ever recommend any Microsoft product. And just in case you miss Jenkins in the above list: I have written about Jenkins here. Enough said.

CI/CD servers in this survey

For each CI/CD server listed here, there is a brief summary of the server, about its documentation, installation options and procedures (for on-premise servers), availability of free plans, and its EULA.

A free plan is not only interesting for open-source projects and startups with a tight budget, but also for companies that want to test a CI/CD server more thoroughly before moving to a paid plan. Trials, if offered, are often limited to 30 or even 14 days, which might not be enough time to gather enough information to serve as a basis for deciding for or against a CI/CD server.

The pricing of CI/CD servers is a science in itself. Including the pricing for paid plans doesn’t seem to make sense to me as these plans can’t be easily be compared.

I’m still looking for a CI/CD server with a small footprint in terms of CPU and RAM. Something that runs on a powerful laptop.

AppVeyor

CI	CD	self-hosted	SaaS

https://www.appveyor.com

AppVeyor is a privately-held Canadian corporation founded in 2011. Their site is well organized, but the latest blog post is from November 2021. Latest AppVeyor version is 7.0.3212, published on April 4, 2022. It seems that development on AppVeyor has stalled.

The site has a status page for the SaaS service, which is updated every month, and is up-to-date.

• hardware requirements - The AppVeyor documentation does not provide system requirements in terms of CPU, RAM, or disk space.
• installation – AppVeyor provides Windows .msi packages, Linux .deb packages for debian and Ubuntu, and can be installed on Macs with Homebrew.
• documentation – The docs could be a bit better organized. Overall, however, the documentation is adequate.
• free plan – The self-hosted Team version is free, with unlimited users, unlimited projects, unlimited concurrent jobs and agents, one team, username/password auth and community support.
  
  The SaaS version comes with a free plan for OSS projects with unlimited public projects, 1 concurrent job, 5 self-hosted jobs, and community support.
• EULA – Quite long, but at least well-structured.

Bamboo Data Center

CI	CD	self-hosted	SaaS
			x

https://confluence.atlassian.com/bamboo/

Bamboo is made by Atlassian and therefor nicely integrates with their other products, most notably, BitBucket and Jira. Its first release was in 2007, it is well known, has a good feature set, and works well. But Being phased out, it is no longer an option for new setups of a CI/CD server.

• supported platforms – Linux, macOS and Windows.

hardware requirements

The Bamboo documentation provides pretty much detailed requirements for different scenarios:

• for small teams with litte concurrent building, 10-20 plans and light server use, a 4 core CPU and 4 GB RAM are recommended
• for medium teams with medium concurrency, 10-20 plans and light server use, an 8 core CPU and 8 GB RAM, and remote agent use are recommended.
• for multiple small teams/one large team, 20-100 plans, high concurrency and medium server use, an 8 core CPU, 16 GB RAM, and more remote agents are recommended
• for departments with 1000s of plans, frequent plan branches, high concurrency and high server use,
  a 16 core CPU, 16 GB RAM, and remote only agents is recommended.

installation

For evaluation, the built-in H2 database is sufficient. For productive environments, a Bamboo installation requires a DBMS and supports PostgreSQL, MySQL, MSSQL and Oracle. In addition, a Java JDK is required. The installation steps are:

• downloading Bamboo and extracting the .tar.gz on Linux/macOS, .zip on Windows.
• edit a config file to set the ‘bamboo.home’ variable.
• start the Bamboo server with a shell script.
• follow the instructions off the setup wizard.

misc

• documentation – Simply excellent.
• trial – Atlassian offers a 30-day trial with unlimited functionality for self-hosted Bamboo.
• free plan Atlassian does not offer free plans, but offers special pricing to eligible entities. I.e., nonprofits and social enterprises, students and teachers, academic institutions and Open Source projects might be eligible for special prices reduced up to 75%.
• EULA – Vast, but easily navigable.

BitBucket Pipelines

CI	CD	self-hosted	SaaS
		x

https://www.atlassian.com/de/software/bitbucket/features/pipelines

BitBucket, a Git-server made by Atlassian, includes BitBucket Pipelines, which replaces the Bamboo Data Center CI/CD server.

BitBucket Pipelines’ core functionalities are similar to those of Bamboo. However, BitBucket Pipelines architecture and workflow is different to Bamboo. The following table list the differences I found most notable:

feature	Bamboo Data Center	Bitbucket Pipelines
pipelines configuration	GUI or YAML/Java Specs	YAML only (bitbucket-pipelines.yml, defined in repo)
multi-repo-builds	native support for multi-repo builds	primarily focused on one repo, reduced multi-repo supports with scripts
separate CI and CD projects	yes	no
scaling	manual agent management	automatic scaling, self-hosted runners can be included

BitBucket Pipelines seems to be easier to manage than Bamboo, but it does not yet offer the same flexibility or full range of features as Bamboo.

misc

• documentation – very good.
• free plan / trial – BitBucket Pipeline options include the free plan BitBucket Free, limited to a max. of 5 users, 1GB workspace storage and 50 build minutes per month. For BitBucket Standard and BitBucket Premium, trials are available.
• EULA – Vast, but easily navigable.

BuildKite

CI	CD	self-hosted	SaaS
		x

https://buildkite.com/home/

Made by an Australian based company, BuildKite includes a package registry.

• documentation – Somewhat use-able, but I find it hard to get the whole picture from the docs. The documentation# includes a set of best practices.
• free plan – The BuildKite Personal plan is free, with 3 concurrent jobs, 1 user, and 90-day retention of data. However, in the paid Pro and Enterprise plan, you get billed a monthly basic fee per active user/month, plus for concurrent agent usage and for managed tests. From the pricing page I cannot deduct if the billing for concurrent agent usage and for managed test applies to the free Personal plan as well.
• trial – 30-days trial with unlimited pipelines, test-suites and package registries. The trial supports up to 200k self-hosted concurrent agents and comes with 2000 CPU-minutes (on Linux).
• EULA – Heavily long-winded.

BuildMaster

CI	CD	self-hosted	SaaS
			x

https://docs.inedo.com/docs/buildmaster/

With BuildMaster’s integration to issue trackers, deployments can be blocked depending on ticket status in the issue tracker. According to the documentation, BuildMaster appears to be geared more toward Windows than toward Linux or macOS.

An interesting feature of BuildMaster is its built-in functionality to build, push and manage Docker images.

• supported platforms – Linux and Windows.
• hardware requirements
  • For Windows, minimum is 2 CPU cores, 4 GB RAM, recommended average/typical is 2 CPU cores, 8 GB RAM, recommended large is 4 CPU cores, 16 GB RAM.
• For Linux Docker installations, a minimum of 2 CPU cores, 2 GB RAM is recommended,
  recommended average/typical - 2 CPU cores, 4 GB RAM, recommended large is 4 CPU cores, 8 GB RAM.
• installation – For Linux, Inedo provides Docker images. For Windows, Inedo recommends installing BuildMaster with InedoHub, a lightweight Windows application, but also provides .exe installers.
• documentation – Easy to navigate, covers all aspects.
• free plan – BuildMaster offers a free plan with unlimited users, unlimited applications, and unlimited servers. All logged-in users are administrators. No LDAP integration, and you can only use their public forums for support.
• EULA – The EULA is eight paragraphs in less than one page, straightforward and simple to understand. Pretty cool.

Buddy

CI	CD	self-hosted	SaaS
		x

https://buddy.works

Buddy is made in BDY PSA, Poland. Which means that their service is bound to the term of the GDPR. Which is cool for businesses as well as for private users, especially for those that are located in Europe.

• documentation – straightforward and all topics are easily accessible. Comes with examples of workflows for all major programming languages, and even for the static site generators Hugo and Jekyll. What’s missing is an introduction into Buddy’s concepts and the basic structure of a CI/CD in Buddy.
• free plan – BuddyWorks offers no free plan.
• trial – Buddy offers a free trial for 14 days, with 1 job, 300 pipeline GB-minutes, 1 GB of pipeline cache, 300 sandbox CPU-minutes, 730 sandbox GB-hours, and no limit on disk space. The trial period ends 14 days after registering. Once the trial period ends, the workspace will be read-only until you subscribe to a paid plan.
• EULA – Buddy’s EULA could be quite a bit shorter if it would not include the system requirements and would not discuss what CI/CD and a pipeline is and how it works. Aside of that, it’s quite shorter than most the EULAs of the other CI/CD servers listed here, and an easy read.

CloudBees CI

CI	CD	self-hosted	SaaS
		x

https://www.cloudbees.com

The site is confusing. There’s CloudBees CI, CloudBees CD/RO and CloudBees Unify. Are these three separate products or are these just feature sets rolled into one product? I couldn’t figure out.

• documentation – The documentation is not well organized and is littered with praises of CloudBees CI all over the place. Perfectly suitable for pissing off devs.
• pricing – You have to contact sales for pricing.
• free plan / trial – Nope. But can try it out with a test instance, or you can book a demo.
• EULA – Comes in two vast documents.

CircleCi

CI	CD	self-hosted	SaaS
		x

https://circleci.com/

installation

There is a self-hosted option, but the requirements for the self-hosted option installation are such that a self-hosted option is not really feasible. Apart from a container registry and a Kubernetes cluster, you need a S3 compatible object storage system, GitHub Enterprise and Nomad Virtual Machines. Which is why I didn’t include the self-hosted option for CircleCI.

• documentation – comprehensive, covers all aspects, well organized and easy to navigate.
• free plan – for the SaaS option, there is an unlimited free plan for the SaaS option, including 5 active users, 30x concurrency and 6000 build-minutes per month.
• EULA – Long-winded, with archaic phrasing like “You shall pay us the Fees set forth in each Order, under the terms set forth therein and this Agreement.” adding to the EULA’s length. At last, a sidebar with a ToC with links makes their EULA easier to navigate.

Drone

CI	CD	self-hosted	SaaS
			x

https://www.drone.io

I’ve test-drove Drone some years ago. Couldn’t wrap my head around how it works. Time for a revisit.

The lastest blog post on the Drone site is from August 5, 2020. The project doesn’t seem to be really active.

• installation – Drone provides Docker images for installation.
• documentation – The documentation still sucks. It’s the worst piece of docs in all the CI/CD systems listed here. No discussion of the basic concepts in Drone. It’s just a setup guide and some reference documentation (i.e. the Drone config vars). The site is confusing as well.
• free plan – There’s a free unlimited plan for self-hosted Drone. But that lacks quite some features: no PostgreSQL or MariaDB, no BLOB storage like Amazon S3, no scheduling. It’s limited to single-machine, comes only with the pipeline plugin and the features to manage secrets are reduced to, well, no managed secrets at all (per-repo, per-org), but just encrypted passwords.
• EULA – Drone’s EULA includes a phone-home functionality of its software, which Drone may use to “monitor Customer’s compliance with this Agreement and improve the Software; and (ii) to create and distribute reports and materials about Drone’s products and services, …” and further “To the extent that this information constitutes personal data, Drone shall be the controller of such personal data.” (Section 2.2). Section 11.10 reads “Customer will keep and maintain complete and accurate records to verify that Software is used in accordance with the scope of the license in this Agreement …” and “Drone may, from time to time, and no more frequently than once every six months during the Term and once within six months of this Agreement’s termination or expiration, request that Customer provide all relevant records necessary to ascertain Compliance”.
  
  This is some of the nastiest shit I’ve ever read in an EULA.

GitLab

CI	CD	self-hosted	SaaS

https://about.gitlab.com/

Another monolithic, enterprisey CI/CD server. Comes with git server, CI, CD, issue tracker, time tracker, wikis, todo lists, and tools for planning projects. Heck, it even has a CRM system included!

• hardware requirements – at least 40 GB of disk space for a basic GitLab installation with no repository data. For a maximum of 20 requests per second or 1,000 users you need an 8 vCPU and 16 GB RAM. You need PostgreSQL (GitHub only supports PostgreSQL), and either Redis or Valkey.

installation

You can run GitLab on-prem, but prepare for providing dedicated hardware. Even when not in action, GitLab hogs memory and CPU cycles like crazy (I test-drove the CE version once for about a week).

Gitlab offers the following installation methods:

• Linux packages for Alma Linux, Amazon Linux, Debian, Ubuntu, Red Hat Enterprise Linux, Oracle Linux, and SUSE Linux Enterprise Server.
• Docker image that includes all components necessary to run GitLab.
• Helm Chart.
• Kubernetes Operator.
• for those with too much time on their hands, you can even install GitLab by compiling it from source.

documentation

As vast as you’d expect for such a monolithic beast. It is comprehensive, really well written, and well organized. I found it much easier to navigate than the documentation of other monolithic monsters that include CI/CD.

The documentation for installation gives various hints how to tune PostgreSQL for GitLab, including how to set some PostgreSQL’s configuration parameters, and provides good information how to monitor GitLab with Prometheus.

free plan

GitLab SaaS offers a free plan for individuals working on personal projects and open source contributions, with Source Code Management, CI/CD, 5 licensed users, 400 compute minutes per month and 10 GiB storage. You can buy additional compute minutes.

GitLab CE (community edition) on-premise is free for individuals working on personal projects and open source contributions.

EULA

The GitLab EULA is long-winding and not an easy read, to say the least. It comes in several documents. The Subscription Agreement alone is several meters of paper if you’d print it. And it doesn’t include the Acceptable Use Policy EU Data Act Supplemental Terms, GitLab Privacy Statement GitLab Data Processing Addendum and Standard Contractual Clauses (GitLab Processing Personal Data from an Enterprise) and the DMCA Notice and Take Down.

GoCD

CI	CD	self-hosted	SaaS

https://www.gocd.org/

GoCD originated at and was funded by Thoughtworks. It evolved from the closed-source, commercial product CruiseControl, the first CI/CD server ever. CruiseControl was renamed to Go, and later renamed to GoCD, to distinguish it from the increasingly popular programming language Go. In 2014, Thoughtworks open-sourced GoCD under the Apache License Version 2.0, and made it available for free.

In 2026, GoCD has a small but active maintainer group who are driving development and are supporting the community. Given the small maintainer group, there is still considerable activity on the GitHub repo, and moderate activity in GoCD forum. Thoughtworks still graciously provides some basic funding, i.e. for infrastructure. At the time of writing the last stable release is version 25.4.0, released on Dec. 31 2025.

GoCD doesn’t come with any built-in special features, but seems to provide a solid foundation on which you can build a CI/CD system. There are quite some integrations in the form of plugins, some of them provided by the GoCD community.

hardware requirements

The minimum requirements are 1 GB RM (2 GB RAM recommended), 2 CPU cores 2GHz, and 1 GB disk space. For Agents, the minimum requirements are 128 MB RAM (256 MB RAM recommended) and 2 GHz CPU. GoCD recommends a separate partition for storing GoCD artifacts.

installation

GoCD provides installers for Windows and macOS. For Linux, GoCD provides RPM and DEB packages. In case your OS is not covered by a GoCD installer or Linux package, GoCD provides a generic ZIP file.

Additionally, GoCD provides Docker images based on AlmaLinux, Alpine, Fedora, CentOS, Debian, Ubuntu and WolfiOS, and a Kubernetes Helm chart.

GoCD supports H2, MySQL and PostgreSQL databases.

misc

• documentation – Starting with a good introduction into GoCD’s basic concepts, it covers all aspects, is easy to navigate and a good read.
• free plan – GoCD is open-source and free to use for everyone. For Businesses: there is no commercial support.
• EULA – GoCD is distributed under the Apache License Version 2.0.

Semaphore

CI	CD	self-hosted	SaaS

https://semaphore.io

Semaphore emphasises on its speed.

installation

• hardware requirements – 8 core CPU and 16 GB RAM. Details on harddisk space are not provided.

Semaphore can be installed on a single machine or an in Kubernetes Cluster in the Google Kubernetes Engine or in the AWS Elastic Kubernetes Service. The single machine installation on bare metal requires K3S (a lightweight Kubernetes) or, optionally, K9s (a Kubernetes CLI).

Semaphore highly recommends installing Semaphore on a subdomain, stating that Installing Semaphore on your base domain might interfere with other services running on the same domain. This somewhat strange.

What I like about the installation process is, that for the setup, instead of being an afterthought, TLS is mandatory.

misc

• documentation – Comprehensive and well organized. I.e., the installation instruction provides all details for setting up a subdomain, and how to issue and install TLS certificates.
• free plan – Semaphore provides a free feature-reduced Community Edition for self-hosting.
• trial – Semaphore offers a free trial account with full functionality for Semaphore Cloud. I haven’t been able to find any information on the maximum length of the trial period.
• EULA – Heavily long-winded.

TeamCity

CI	CD	self-hosted	SaaS
	x

https://www.jetbrains.com/teamcity/

Another veteran CI server. TeamCity was launched in 2006, shortly after Hudson (which later became Jenkins), and succeeded precisely where Hudson had failed (and Jenkins still fails): it was easy to configure and manage.

The TeamCity site’s homepage reads “Powerful CI/CD solution for modern DevOps teams”. Which a bit misleading, because TeamCity is just a CI server. While you can extend it into a full CI/CD server with some effort, for small teams up to 5 devs, I wouldn’t bet on it as a full CI/CD server for larger teams or even a small team with complex build and deployment setups.

The CI part is where TeamCity really shines. Installation is painless and its works out of the box with a polished interface. For those who prefer to work on the commandline, TeamCity also provides a CLI for Windows, macOS and Linux.

hardware requirements

The documentation provides the hardware requirements for different, very detailed scenarios, including

• number of projects, number of build configurations (assumed that a quarter of them is running regularly),
• number of builds per day, size of log per build, number of build agents, number of web and IDE users, number of VCS roots
• number of changes per day.

To cut things short, with a 3.2 GHz dual-core CPU, 8 GB RAM and an 1 GB network adapter you’re good to go with up to 30-50 users.

installation

TeamCity offers several options for installation on Windows, macOS and Linux: Docker images, tar.gz archives, and an installer for Windows. The tar.gz archive comes bundled with Tomcat, and with a build agent and a startup script which allows for easy TeamCity server evaluation with one agent.

The installation process suitable for a TeamCity test-drive, using the tar.gz archive, is simple. Assuming an installation on Linux, the following will do:

• download the tar.gz archive and expand it into the TeamCity installation directory (i.e., somewhere in /opt).
• create a user for running TeamCity (i.e, user teamcity).
• optional – change the default port of the TeamCity server (default is port 8111).
• as the TeamCity user, cd into the installation and run the startup script.

For productive environments, TeamCity provides an installer for the TeamCity server for Windows, a .tar.gz archive for macOS and Linux, and docker files for Windows and Linux. Agents can be installed with the server UI, which also provides an agent push functionality to install agents on remote machines. The push functionality works with SSH and SSH keys installed on both the server and the remote machine, and with password authentication.

misc

• documentation – TeamCity comes with a decent, comprehensive and very detailed documentation.
• free plan – The self-hosted TeamCity Professional Server is free to use with full access to all features, limited to 3 build agents and up to 100 build configurations. The SaaS version of TeamCity doesn’t offer a free plan. Students and Teachers can get free educational licenses (can’t be used for commercial work). User groups and oen source project might be eligible for a free license as well.
• EULA – I wasn’t able to find TeamCity’s EULA on their website.

Travis CI

CI	CD	self-hosted	SaaS

https://www.travis-ci.com

From its name, I assumed Travis CI to be a CI-only server. But the documentation shows that Travis CI is a full CI/CD server. I haven’t followed the history of Travis CI, but I guess the CD functionality has been added somewhere on the way.

There is Travis CI, the SaaS option, and there is Travis CI Enterprise, the self-hosted option of Travis.

The activity around Travis CI seems to slow down. The blog on the website was quite active, but the latest blog post is from May 2025. There’s a bit more activity on the forum.

For using the SaaS version of Travis CI, a GitHub, Assembla, Bitbucket, or GitLab account is mandatory.

Information on the on-premise option Travis CI Enterprise, apart from contact to sales, is hard to find on the site.

hardware requirements

I couldn’t find the hardware requirements for Travis CI Enterprise.

documentation

The documentation is comprehensive and covers all aspects, but is a bit messy. It took me some time to stumble across the documentation for Travis CI Enterprise, the link is to it is hidden somewhere in the Travis CI docs. This is how I learned about Travis CI Enterprise, the on-premise solution of Travis CI by accident. The Travis CI community can contribute to the docs through the Travis CI docs GitHub repo.

misc

• free plan / trial – At first, I couldn’t find a free plan or a trial option on the travis CI site. You can book a demo. Hidden in the documentation for Travis CI Enterprise is a note that you can get a trial license, but it is not stated how to get that license. I guess you have to contact sales for that.
• EULA – The EULA for the SaaS travis CI is six pages, for the on-prem travis CI it’s 5 pages. Small font, and long-winded.

Conclusion: the good, that bad, and the ugly

This is certainly heavily biased. First, I separate the wheat from the chaff. From checking out the website, the documentation, installation options (for on-premise) and procedures, the feature set, and the EULA, I wouldn’t give 4 CI/CD servers of the 14 servers listed here a first try.

CI-only servers, on-premise

• TeamCity – there is no alternative to TeamCity, except self-hosted full CI/CD servers, which of course you can use for CI only, too. The Professionell Edition is free to use on-premise, even for Businesses, limited to 3 agents and 100 build configurations. This should cover the needs of small teams, and should be enough for larger teams to test-drive TeamCity for a while. The on-prem setup is painless, and has a pretty low maintenance overhead.

CI-only servers, SaaS

• TeamCity – again, TeamCity is without alternative here.

CI/CD servers, on-premise

• Bamboo – an outstanding CI/CD server, with integration to other Atlassian Products, especially BitBucket and Jira. Unfortunately, the final end-of-life for Bamboo Data Center is planned for March 2029, and Bamboo will be replaced by the SaaS solution BitBucket Pipelines. So, for new setups, Bamboo is not an option. Organizations already using Bamboo have to migrate to BitBitBucket Pipelines or have to look for other solutions.
• BuildMaster – to me, it seems that this CI/CD solution is geared toward SMEs. The hardware requirements are moderate. For those that don’t mind the additional level of abstraction that comes with Docker, BuildMaster might be a good choice. The free plan is only suitable for small teams that don’t mind that every logged-in user has full administrative access.
• GitLab – is an excellent option, if you don’t mind its appetite for CPU cycles and RAM.
• GoCD – a quite simple and straight-forward CI/CD server, providing a good base to build a CI/CD server for your requirements. Comes with a lot of installation options (directly on bare metal from installation archives, Docker images, Linux packages, and Windows and macOS installers). The hardware requirements are moderate. GoCD is completely free to use, which makes it a good option for small teams/private projects, startups with a tight budget, and open-source projects.
• Semaphore – the setup of the self-hosted version is more complicated than necessary, because it requires Kubernetes or the lightweight Kubernetes solution K3s. An additional level of abstraction for everything is not everyone’s cup of tea. If you don’t mind the dependence on Kubernetes, Semaphore looks like a good option.

CI/CD servers, SaaS

• BitBucket Pipelines - replaces Atlassian’s self-hosted CI/CD server Bamboo, which is being phased out. It seems to be easier to manage than Bamboo, but is doesn’t offer the full functionality of Bamboo. For complex scenarios, like multi-repo builds, this is a setback.
• Buddy – Located in Poland, Europe, Buddy BDY SPA is bound to the GDPR, which is a valuable feature, especially for companies located in Europe
• BuildKite the only thing that differentiates this CI/CD server from its competitors is an included package registry.
• Circle-Ci – Its free plan with 5 users and 30x concurrency might make it interesting for open-source projects and startups with a tight budget, as long as the 200 build minutes per day cover your needs.
• GitLab – has an extensive feature set and is an excellent choice.
• Semaphore – looks like a good option.

CI/CD servers I don’t recommend

• AppVeyor – seems to be dead in the water.
• CloudBees CI – seems that this company doesn’t want to sell its product or service. First they work hard on confusing potential customers with their website. If that doesn’t work, they do their best to piss off the customer’s devs with the documentation.
• Drone – the documentation sucks. The free plan is limited in functionality in such a way that anything apart from a very basic test-drive makes no sense with the free plan.
• Travis CI – from the information on their website, Travis CI doesn’t offer anything you could get from other solutions. The drawbacks here is that both activity around Travis seems to have slowed down, and there are no free plans to check out Travis, and it’s unclear how to get a trial. The documentation on the on-premise option is hard to find.