Websites, blogs, and social media are defined as follows in CMOS 14.205:
"Website refers to the collection of pages (web pages) made publicly available via the internet at a specific location on the World Wide Web by an individual or an organization."
"A blog (from weblog) is a web-based forum that consists of posted entries organized by date or topic (and often also titled or signed or both) and usually accompanied by readers' comments."
"Social media (or social networking) refers to any internet based forum for public communication shared by means of a dedicated platform or service."
CMOS acknowledges that the lines between these forms can be murky, so how you create your citations for your sources will often require a judgment call on your part.
Note that the intention for this guide page is to cover uniquely web content. Other pages of this guide include web based content when it makes sense for those pages.
The main elements of a bibliography entry for a website or webpage follows many of the general rules, but there are differences, particularly regarding access date and time (CMOS 14.206-14.207):
Webpage author(s) (if applicable). "Webpage title" (if applicable). Website title or description. Website owner or sponsor. Date of publication, last modification, or access date, and timestamp (if applicable). URL.
A webpage with a title but no author:
"The History of the Vatican Museums." Vatican Museums. Directorate of the Vatican Museums. Accessed July 23, 2018. http://www.museivaticani.va/content/museivaticani/en/musei-del-papa/storia.html.
A website identified as such:
"About." Bubba Ho-Tep (website). Silver Sphere Corporation. Accessed August 6, 2018. http://www.bubbahotep.com/aboutbht.html.
A webpage with a timestamp:
Grady, Constance. "Meet a New Kind of Book, Designed for the Age of Peak TV." Vox. Vox Media. August 6, 2018, 10:00 a.m. https://www.vox.com/culture/2018/8/6/16849756/serial-box-serialized-books-peak-tv.
The main elements of a bibliography entry for blog postings follow many of the general rules for newspaper articles (for guidance specific to newspaper articles see "Newspaper Articles - Basic Rules") (CMOS 14.208):
Post author(s) (if applicable). "Post title" (if applicable). Blog title. Larger publication blog is part of (if applicable), date of post. URL.
Article from a blog identified as such and that is part of a larger publication:
Krasinski, Jennifer . "Why Did Google Erase Dennis Cooper’s Beloved Literary Blog?" Culture Desk (blog). The New Yorker, June 24, 2016. https://www.newyorker.com/culture/culture-desk/why-did-google-erase-dennis-coopers-beloved-literary-blog.
Citation for an entire blog without an editor:
Culture Desk (blog). The New Yorker. https://www.newyorker.com/culture/culture-desk.
Citation for an entire blog with an editor:
Lamberty, Anthony, ed. Eat Sleep Draw (blog). http://eatsleepdraw.com/.
The main elements of a bibliography entry for a social media post follow many of the general rules, but are unique in author screen name is included, title is replaced by text from the post, and social media service is used as larger work title (CMOS 14.209):
Post author(s). "Post text." Type of post, date of post. URL.
Posting by an organization:
Smithsonian. "The beer fridge of 1899 is ready for a summer party. It had places for kegs to rest, plus shelves in the lower part could be removed for more room." Facebook. August 1, 2018. https://www.facebook.com/Smithsonian/posts/10156728532859574.
Posting with real name and screen name:
Obama, Barack (BarackObama). "We remember everyone we lost on 9/11 and honor all who defend our country and our ideals. No act of terror will ever change who we are." Twitter, September 11, 2017. https://twitter.com/BarackObama/status/907265689832103936.
Posting for an image:
Phillips, Jeffrey D. (jeff_the_peff). "Sneaky sketches." Instagram drawing. July 3, 2018. https://www.instagram.com/p/BkwmlzFDnBD/?taken-by=jeff_the_peff.