By contributing you agree to respect the [Code of Conduct](https://github.com/EbookFoundation/free-programming-books/blob/master/CODE_OF_CONDUCT.md) of this repository.
1. "A link to easily download a book" is not always a link to a *free* book. Please only contribute free content. Make sure it's free. We do not accept links to pages that *require* working email addresses to obtain books, but we welcome listings that request them.
2. You don't have to know Git: if you found something of interest which is *not already in this repo*, please open an [Issue](https://github.com/EbookFoundation/free-programming-books/issues) with your links propositions.
- If you know Git, please Fork the repo and send pull requests.
- *Courses* : A course is a learning material which is not a book. [This is a course](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-006-introduction-to-algorithms-fall-2011/).
- *Interactive Tutorials* : An interactive website which lets the user type code or commands and evaluates the result (by "evaluate" we don't mean "grade"). e.g.: [Try Haskell](http://tryhaskell.org), [Try Github](http://try.github.io).
- *Problem Sets & Competitive Programming* : A website or software which lets you assess your programming skills by solving simple or complex problems, with or without code review, with or without comparing the results with other users.
5. GitHub Actions will run tests to make sure your lists are alphabetized and formatting rules are followed. Be sure to check that your changes pass the tests.
- use the link with the most authoritative source (meaning the author's website is better than the editor's website, which is better than a third party website)
- always prefer a `https` link over a `http` one -- as long as they are on the same domain and serve the same content
- on root domains, strip the trailing slash: `http://example.com` instead of `http://example.com/`
- always prefer the shortest link: `http://example.com/dir/` is better than `http://example.com/dir/index.html`
+ no URL shortener links
- usually prefer the "current" link over the "version" one: `http://example.com/dir/book/current/` is better than `http://example.com/dir/book/v1.0.0/index.html`
- if a link has an expired certificate/self-signed certificate/SSL issue of any other kind:
1.*replace it* with its `http` counterpart if possible (because accepting exceptions can be complicated on mobile devices).
2.*leave it* if no `http` version is available but the link is still accessible through `https` by adding an exception to the browser or ignoring the warning.
+ if they link to different editions, and you judge these editions are different enough to be worth keeping them, add a separate link with a note about each edition (see [Issue #2353](https://github.com/EbookFoundation/free-programming-books/issues/2353) to contribute to the discussion on formatting.)
- prefer atomic commits (one commit by addition/deletion/modification) over bigger commits. No need to squash your commits before submitting a PR. (We will never enforce this rule as it's just a matter of convenience for the maintainers)
- if an email address or account setup is requested before download is enabled, add language-appropriate notes in parentheses, e.g.: `(email address *requested*, not required)`
While the basics are relatively simple, there is a great diversity in the resources we list. Here are some notes on how we deal with this diversity.
#### Metadata
Our lists provide a minimal set of metadata: titles, URLs, creators, platforms, and access notes.
##### Titles
- No invented titles. We try to take titles from the resources themselves; contributors are admonished not to invent titles or use them editorially if this can be avoided. An exception is for older works; if they are primarily of historical interest, a year in parentheses appended to the title helps users know if they are of interest.
- International URLs should be escaped. Browser bars typically render these to Unicode, but use copy and paste, please.
- Secure (https) URLs are always preferred over non-secure (http) urls where https has been implemented.
- We don't like URLs that point to webpages that don't host the listed resource, but instead point elsewhere.
##### Creators
- We want to credit the creators of free resources where appropriate, including translators!
- For translated works the original author should be credited.
- We do not permit links for Creators.
- For compilation or remixed works, the "creator" may need a description. For example, "GoalKicker" books are credited as "Compiled from StackOverflow documentation"
- Courses. Especially for our course lists, the platform is an important part of the resource description. This is because course platforms have different affordances and access models. While we usually won't list a book that requires a registration, many course platforms have affordances that don't work without some sort of account. Example course platforms include Coursera, EdX, Udacity, and Udemy. When a course depends on a platform, the platform name should be listed in parentheses.
- YouTube. We have many courses which consist of YouTube playlists. We do not list Youtube as a platform, we try to list the Youtube creator, which is often a sub-platform.
- YouTube videos. We usually don't link to individual YouTube videos unless they are more than an hour long and are structured like a course or a tutorial.
- Leanpub. Leanpub hosts books with a variety of access models. Sometimes a book can be read without registration; sometimes a book requires a Leanpub account for free access. Given quality of the books and the mixture and fluidity of Leanpub access models, we permit listing of the latter with the access note *(Leanpub account or valid email requested)*
#### Genres
The first rule in deciding which list a resource belongs in is to see how the resource describes itself. If it calls itself a book, then maybe it's a book.
##### Genres we don't list
Because the Internet is vast, we don't include in our lists:
- blogs
- blog posts
- articles
- websites (except for those that host LOTS of items that we list.)
- videos that aren't courses or screencasts.
- book chapters
- teaser samples from books
- IRC or Telegram channels
- Slacks or mailing lists
Our competitive programming lists are not as strict about these exclusions. The scope of the repo is determined by the community; if you want to suggest a change or addition to the scope, please use an issue to make the suggestion.
##### Books vs. Other Stuff
We're not that fussy about book-ness. Here are some attributes that signify that a resource is a book:
Courses often have associated textbooks, which we would list in our books lists. Courses have lectures, exercises, tests, notes or other didactic aids. A single lecture or video by itself is not a course. A powerpoint is not a course.
- Formatting rules enforcement is automated via [GitHub Actions](https://github.com/features/actions) using [fpb-lint](https://github.com/vhf/free-programming-books-lint) (see [.github/workflows/fpb-lint.yml](.github/workflows/fpb-lint.yml))
- If you specify more than one file, results of the build are based on the result of the last file checked. You should be aware that you may get passing green builds due to this so be sure to inspect the build log at the end of the pull request by clicking on "Show all checks" -> "Details".
