Can’t remember some obscure HTML tag detail, Apache directive or C++ function? There’s endless technical documentation on the web, so entering a few keywords at Google will probably tell you all you need.
Web-based solutions aren’t always the best, though. You’ll need to be online. Sites may be slow and unresponsive. Documentation quality will vary, and every site works differently.
Zeal is an offline software documentation browser covering almost 200 APIs, languages, applications and tools.
The download doesn’t include any of these, but they’re simple to download. Go to File > Options > Docsets, check the boxes next to anything interesting in the “Downloadable docsets” box and click Download.
Whatever you’re chosen is displayed in a tree. Some docsets are essentially just references (HTML has 484 pages on attributes, 138 on tags), while others have helpful guides (the Apache file covers everything from .htaccess files to “When NOT to use mod_rewrite”).
Start typing a particular keyword in the search box and Zeal displays hits in every open docset.
Alternatively, entering a query like “html:bgcolor” allows searching a single docset only.
This was all very quick and easy for us,much faster and more lightweight than a browser equivalent (RAM use was barely 70MB, even with multiple docsets open). If you find the product useful, there are plugins which allow it to be used from within various editors and IDEs: Atom, Brackets, Emacs, Sublime Text and more.
Zeal is a free tool for Windows and Linux.