When comparing Codacy vs Coveralls, the Slant community recommends Coveralls for most people. In the question“What are the best code coverage services?” Coveralls is ranked 3rd while Codacy is ranked 5th. The most important reason people chose Coveralls is:
Coveralls offers unlimited free support for open source projects.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free for open-source projects
Pro Tons of features, plugins to check code
The list is never ending: they use a lot of open sourced linters for many different languages, allowing to configure them one by one, add custom rules... It checks duplicates, issues, security AND is customizable.
Pro Free for open source
Coveralls offers unlimited free support for open source projects.
Pro Maturity
Coveralls is older than Code Climate and already supports 21 languages. It also seems like it's the most popular given how new some of the other services are, which is great for support.
Cons
Con Reports tons of noisy, irrelevant "quality" metrics
You want code coverage, not someone to tell you where to put semicolons in your markdown documents. It spots dozens of "issues" in your code and Markdown sources, none of which are in any way valid, most of which were random opinions from people with no justification and not accepted best practices. (In fairness, on the Python side, this was due largely to Pylint itself being way too prescriptive.)
Con Can't handle combined coverage
When there are multiple environments that contribute coverage to different branches it just picks one at random and says that the rest of the code isn't covered at all.
Con Dashboard causes Safari to freeze, crash
Con API Tokens need to be hard coded
Most CIs have options for that in safe environment variables, but that makes it unavailable in PRs anyways. The support says they're working on it.
Con Terrible support
Con The user interface is hard to understand
Con It's defective and integration doesn't work properly
Con Poor tooling
Depending on your language the tooling is practically abandonware.
Con No support for common coverage report stadards
They accept their own format over their own HTTP API. Other services allow the uploading of standard reporting formats and parse them internally.
