Can I use a username as the author?

Yes. The University of Sheffield's Harvard guide says so directly: if the author of a post has used an alias instead of their real full name, you may use it in both the in-text citation and the reference. Murdoch University's APA guide and the MLA Style Center both publish examples whose authors are usernames.

How do I cite a reply rather than the original post?

Cite it in relation to the post it answers. Murdoch's APA guide gives the reply's own author and date, then "[Response to the forum post …]"; the MLA Style Center's Reddit example begins "Comment on …"; and the Chicago Citation Quick Guide states that comments are cited in reference to the original post.

What if the post has no title?

Describe it. The Chicago Citation Quick Guide's rule for social media content is to quote up to the first 280 characters of the post in place of a title; MLA's Reddit example supplies a description of the post's content. Either way the description is yours, so keep it factual.

Is a forum post a good source?

It is evidence of what someone said, not evidence that what they said is true. Cite it when the post itself is your object of study — a user's account of a problem, a community's reaction, a maintainer's explanation. Do not cite it as authority for a technical or clinical claim; go to the documentation or the literature for that.

What if the thread is deleted or edited later?

Give the date you accessed it, which is exactly why Harvard and IEEE templates ask for one, and keep your own copy or an archive link. Forum titles and posts can be edited after the fact, and the version you read may not be the version your reader finds.

How to Cite a Forum or Reddit Post

Forums are cited more often than style manuals admit — in software engineering, in health research on patient communities, in any study of how people talk to each other online. The information a reference needs is stable across styles: who posted, under what name, in which thread, on which board, on what date, and a link that resolves to that post rather than to the board.

The worked example is a real forum post, verified on 22 September 2026 through the Stack Exchange API: the Stack Overflow question "Why is conditional processing of a sorted array faster than of an unsorted array?", posted by the user GManNickG on 27 June 2012, at stackoverflow.com/questions/11227809/.

What to Collect

The username or real name of the poster, as displayed
The title of the thread or post
The name of the forum, board or subreddit
The name of the wider platform, where it differs from the board
The date, and the time where the platform shows one
The permalink to the specific post or comment
The date you accessed it

Quick Reference by Major Style

APA (7th Edition)

APA's Common Reference Examples handout has no forum entry. Murdoch University's APA guide publishes three, and these are its own examples, verbatim — a board, a post and a reply:

LawAnswers. (2023). Criminal Law Forum. https://www.lawanswers.com.au/forums/criminal-law-forum.5/

imaximis (2023, January 17). I bought a car with a false signature [Forum post to Criminal Law Forum]. LawAnswers. https://www.lawanswers.com.au/threads/i-bought-a-car-with-a-false-signature.24578/

Veith, R. (2023, February 1). If you have proof of purchase then you should be at little risk as long as you paid fair market value. [Response to the forum post I bought a car with a false signature]. LawAnswers. https://www.lawanswers.com.au/threads/i-bought-a-car-with-a-false-signature.24578/

Applied to the verified example:

GManNickG. (2012, June 27). Why is conditional processing of a sorted array faster than of an unsorted array? [Forum post]. Stack Overflow. https://stackoverflow.com/questions/11227809/why-is-conditional-processing-of-a-sorted-array-faster-than-of-an-unsorted-array

In-text: (GManNickG, 2012)

MLA (9th Edition)

The MLA Style Center published a post on citing material on a site like Reddit on 21 July 2021. Both entries below are MLA's own, verbatim — the first a post, the second a comment on it. Note MLA's explanation: because the post reviews a book rather than carrying a title of its own, MLA supplies a description that includes the book title.

U/reggiew07. Review of King Leopold's Ghost: A Story of Greed, Terror, and Heroism in Colonial Africa, by Adam Hochschild. Reddit, 31 Oct. 2020, www.reddit.com/r/books/comments/jlbrs4/king_leopolds_ghost_a_story_of_greed_terror_and/.

Varro-reatinus. Comment on U/reggiew07's review of King Leopold's Ghost: A Story of Greed, Terror, and Heroism in Colonial Africa, by Adam Hochschild. Reddit, 31 Oct. 2020, www.reddit.com/r/books/comments/jlbrs4/king_leopolds_ghost_a_story_of_greed_terror_and/.

Those two entries are reproduced from the MLA Style Center; reddit.com itself would not serve a request from this machine, so the underlying post was not re-checked here. Applied to the verified Stack Overflow example, where the post does have a title of its own:

GManNickG. "Why Is Conditional Processing of a Sorted Array Faster than of an Unsorted Array?" Stack Overflow, 27 June 2012, stackoverflow.com/questions/11227809/why-is-conditional-processing-of-a-sorted-array-faster-than-of-an-unsorted-array.

In-text: (GManNickG)

Chicago (18th Edition)

The free Chicago Citation Quick Guide has no forum entry, but it does have one for social media content, and its stated rules transfer: citations can usually be limited to the text; if a reference-list entry is needed, quote up to the first 280 characters of the post in place of a title; and comments are cited in reference to the original post. Chicago's own example of a comment, in-text:

(Michele Truty, April 17, 2015, 1:09 p.m., comment on Chicago Manual of Style 2015)

Applying the social-media pattern to a forum post, which is an adaptation rather than a Chicago-published form:

GManNickG. 2012. "Why is conditional processing of a sorted array faster than of an unsorted array?" Stack Overflow, June 27. https://stackoverflow.com/questions/11227809/why-is-conditional-processing-of-a-sorted-array-faster-than-of-an-unsorted-array.

In-text: (GManNickG 2012)

Harvard (Cite Them Right)

The University of Sheffield Library's Harvard guide, which states that it is based on Cite Them Right, publishes a Forum Post/Message Board entry. Its template and examples, verbatim:

Username or Surname, INITIAL(S). of creator (Year) 'Title/Subject of message', Title of host message system (required if applicable), Day/Month message was posted. Available at: URL or Available email: email address (Accessed: date).

Keith (2019) 'usb wireless adapter for Ubuntu18.04', Linux Forums, 11 July. Available at: https://linuxforums.org.uk/index.php?topic=13634.msg110605#msg110605 (Accessed: 26 May 2021).

McNaught, A. (2021) 'Implementing digital accessibility regulations', DIGITALACCESSIBILITYREGULATIONS, 4 May. Available email: digitalaccessibilityregulations@jiscmail.ac.uk (Accessed: 26 May 2021).

Sheffield's note on usernames is the one to remember: if the author has used an alias, use it in the citation and the reference. Applied to the verified example:

GManNickG (2012) 'Why is conditional processing of a sorted array faster than of an unsorted array?', Stack Overflow, 27 June. Available at: https://stackoverflow.com/questions/11227809/why-is-conditional-processing-of-a-sorted-array-faster-than-of-an-unsorted-array (Accessed: 22 September 2026).

In-text: (GManNickG, 2012)

IEEE

The IEEE Reference Guide has no forum or message-board section. Its closest published forms are Blogs and Websites. The website template, verbatim:

First Name Initial(s) Last Name. "Page Title." Website Title. Date Accessed. [Online]. Available: Web Address.

Applied to the verified example, with the username in the author position:

GManNickG. "Why is conditional processing of a sorted array faster than of an unsorted array?" Stack Overflow. Accessed: Sep. 22, 2026. [Online]. Available: https://stackoverflow.com/questions/11227809/why-is-conditional-processing-of-a-sorted-array-faster-than-of-an-unsorted-array

In-text: [1]

Missing Elements

No date on the post. Some boards show only relative times ("3 years ago"). Hover or open the post's permalink, which usually carries an absolute timestamp. If nothing does, use your style's no-date convention and give the accessed date.

No thread title. Use Chicago's rule — the opening text, up to 280 characters — or a factual description, as MLA does.

A real name behind a username. Use whichever the post displays. Do not deanonymise someone by pairing a pseudonym with a name you found elsewhere; that is a research-ethics question, not a formatting one.

A deleted post. Cite what you have, say it has since been removed, and give the archive URL if you have one.

A mailing-list message rather than a web forum. Sheffield's template covers this: give the list name as the host system and the list address in place of a URL.

Common Mistakes

Linking the board or subreddit instead of the permalink to the post
Citing a reply as though it were the original post
Silently "correcting" a username's capitalisation or dropping a u/ or @ prefix
Using a forum answer as authority for a technical claim instead of the documentation it points to
Leaving out the accessed date on a source that can be edited or deleted
Quoting a post that has since been edited without saying when you read it

Sources for These Formats

Stack Exchange API record for question 11227809 (title, owner, creation date, canonical link), api.stackexchange.com
Murdoch University Library, APA guide: Forum / Discussion Board, Forum Post and Comment on Forum Post
MLA Style Center, "How do I cite material posted on a social media site like Reddit?", published 21 July 2021
The Chicago Manual of Style Citation Quick Guide, Social media content — checked for a forum entry and found not to have one
University of Sheffield Library, "Harvard referencing" (based on Cite Them Right), Forum Post/Message Board
IEEE Reference Guide, sections A (Blogs) and T (Websites) — checked for a forum section and found not to have one
APA Style, Common Reference Examples handout (last updated 3 March 2026) — checked for a forum entry and found not to have one

Full style rules: APA, MLA, Chicago, Harvard, IEEE.