When comparing Velocity vs Zeal, the Slant community recommends Zeal for most people. In the question“What are the best offline documentation browsers?” Zeal is ranked 2nd while Velocity is ranked 6th. The most important reason people chose Zeal is:
You can also download additional "Docsets" if you need them, including ActionScript, JavaScript, OS X, Android, Python and tons of others.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Access over 170 APIs offline
You can also download additional "Docsets" if you need them, including ActionScript, JavaScript, OS X, Android, Python and tons of others.
Pro Filter search by API
Pro Visual Studio Code plugin
Visual Studio Code plugin available.
Cons
Con Outdated
Runs on Windows 7/8, uses old docs from MSDN, Visual Studio 2010, 2012, 2013, 2015.
Con Javascript Docs broken by default
The Javascript Docs are broken by default, they require you to manually fix it yourself rather than do anything about it.