The Vote Math Behind Reddit Best vs Top Comments

What is the difference between Reddit best vs top comments?

The split in Reddit best vs top comments comes down to what each sort measures: Top ranks a comment by its net score, upvotes minus downvotes, while Best ranks it by how sure Reddit can be that most voters liked it. Top rewards volume. Best rewards agreement, and discounts agreement from a small sample.

Reddit's help centre names both sorts and explains neither. The "What mods can do" article lists the six comment sorts a moderator can suggest, Best, Old, Top, Q&A, Controversial and New, and stops there. The formulas come from reddit-archive/reddit, the open-source codebase Reddit stopped updating in 2017. Today's production ranking is closed source, so read everything below as the last published version.

How does the Top sort rank comments?

Top sorts comments by net score and nothing else. The archived _sorts.pyx defines the score in one line, return ups - downs, and the comment sort menu maps top to a descending sort on that value.

Top has no time filter on comments. Reddit's API reference gives /comments/{article} a sort parameter and no t parameter, unlike the post listings. Every comment in the thread competes on its all-time net score, so a comment posted in the first hour holds a head start that a better reply posted on day two has to out-vote in raw numbers. A comment's net score is separate from the profile total that how Reddit karma works describes, although the two move together.

How does the Best sort rank comments?

Best ranks a comment by the lowest share of upvotes it plausibly deserves, given how many votes it has. The archived function is _confidence in _sorts.pyx:

n = ups + downs
z = 1.281551565545  # 80% confidence
p = float(ups) / n
left = p + 1/(2*n)*z*z
right = z*sqrt(p*(1-p)/n + z*z/(4*n*n))
under = 1+1/n*z*z
return (left - right) / under

That is the lower bound of the Wilson score interval, and the function's docstring cites Evan Miller's how-not-to-sort-by-average-rating page on evanmiller.org as the source. p is the observed share of upvotes and n is the total vote count. The right term shrinks as n grows, so a comment with many votes sits close to its real upvote share, while a comment with two votes gets marked down hard for the uncertainty. A comment with no votes scores 0. The archived menu labels this sort "best" and sets it as the default for comment pages, _default = 'confidence'.

How do the two sorts order the same comments?

In opposite directions, when the comments differ in size and agreement. The four comments below run through both formulas from the archived code:

The ranking flips completely. Top puts the big, split comments first because they collected the most net points. Best puts D first because 10 votes out of 10 is strong evidence that readers agree, and it drops A and B because a 55% to 57% upvote share means nearly half the room voted against them. C is the comment that does well under both.

You cannot rebuild this table from a live thread. Reddit's interface shows one number per comment, not separate up and down counts, so the ordering is the only output of the formula you get to observe.

Why does a new comment climb faster under Best?

Because Best needs agreement, not a lead. A reply at 5 up and 0 down scores 0.753 under the archived formula, which already beats comment A at 400 up and 300 down. Under Top, the same reply needs 96 more net points to pass A.

That gap matters to anyone replying by hand in a thread that is already busy. On a thread sorted by Best, a late answer that the first few readers upvote without dissent moves above the divisive comments near the top. On a thread sorted by Top, a late answer stays below every early comment until it out-scores them. The timing side of that problem, when a thread is still worth joining, is covered in the best time to post on Reddit. A single upvote is not enough: a comment at 1 up and 0 down scores 0.378 and ranks below all four comments in the table.

Is Best on comments the same as Best on the home feed?

No. The two sorts share a name and nothing else. Best on a comment page is the confidence formula above. Best on the home feed is a personalised ranking of posts, and Reddit's "What are home feed recommendations?" article describes it as "a personalized sorting option that's continuously being improved", one that "takes some elements of your Reddit activity into account such as whether you tend to like new communities or not, how old or new your account is, and what types of posts you've upvoted or commented on in the past".

The archived comment formula takes no input about the reader. It reads a comment's upvotes and downvotes and nothing else, while home feed Best is built from your own history.

Which sort does a Reddit thread open with?

The one the moderators chose, or Reddit's default when they chose none. Reddit's help centre does not state the current default comment sort. The archived code defaults to confidence, which the interface labels Best.

Moderators have two levels of control. A community-wide default sits in community settings, where Reddit recommends "none" for most communities and names Q&A, top and live as the alternatives for communities with other needs. A per-thread default comes from /api/set_suggested_sort, which the API reference explains with "casual conversation may be better sorted by new by default, or AMAs may be sorted by Q&A". Contest mode overrides both: Reddit's moderator help says it "hides all replies to top-level comments, scrambles all comments, and hides the scores to all comments". Communities can also hide comment scores for up to 24 hours, which Reddit's settings article gives as 1,440 minutes.

Check the sort label above the comments before you treat the first reply as the community's verdict. A thread on Q&A, New or contest mode is not showing you what the most people agreed with.

Which sort should you read when looking for reply opportunities?

Read Top on a finished thread, Best on a live one, and New to find follow-up questions nobody has answered. Top on an old thread shows what the community settled on, which is the answer your reply has to add to rather than repeat. Best on a live thread shows which replies are winning agreement now. New surfaces the "did anyone find a fix?" comments that sit under a dozen upvoted answers.

The sort also decides what you read without clicking. The API reference for /api/morechildren explains that "the most relevant comments are selected for display first", and the rest are stubbed out behind MoreComments links. On a long thread, the comments that mention your category sit behind a "more replies" link under one sort and on screen under another.

RedReplier skips the sort question for keyword matches. RedReplier watches Reddit continuously and surfaces the posts and comments that match your keywords, so you do not pick a sort or expand "more replies" to find the comment that names your keyword. Each match shows the post, the matched keywords, the surrounding comments and the subreddit context. RedReplier never auto-comments: a person reads the thread, checks the subreddit rules, and posts from their own account. Delivery options are on the Reddit alerts page, and the rules that decide whether a reply survives moderation are in Reddit promotion rules.

Frequently asked questions

Is Best or Top the default comment sort on Reddit?

Reddit's help centre does not say. The archived open-source code set Best, internally confidence, as the default for comment pages, and moderators can override it with a suggested sort for a whole community or a single thread.

Why is the top-voted comment not first under Best?

Best ranks by the share of upvotes, adjusted for sample size, not by net score. A comment with 400 upvotes and 300 downvotes has a high net score and a 57% upvote share, so a smaller comment with near-unanimous upvotes outranks it.

Does Top for comments have a time filter?

No. Reddit's API reference gives the comment tree endpoint a sort parameter and no t parameter. Top on a comment page ranks every comment in the thread by its all-time net score.

What does the Q&A comment sort do?

The archived code calls Q&A a variant of Best "specially designed for Q&A-type threads to highlight good question/answer pairs". It adds a question's confidence score to the confidence score of the original poster's best answer, plus a small bonus for text length. Reddit's API reference names AMAs as the use case.

Can a comment with zero downvotes still rank low under Best?

Yes, when it has few votes. A comment at 1 up and 0 down scores 0.378 under the archived formula, below a comment at 250 up and 200 down. The formula treats one vote as weak evidence, and the score rises as more votes agree.

Does contest mode use Best or Top?

Neither. Reddit's moderator help says contest mode "scrambles all comments" and hides their scores, and it hides replies to top-level comments too. The archived code has a random sort that shuffles comments, and Reddit does not document whether contest mode uses it.

How long can a subreddit hide comment scores?

Reddit lets communities hide comment scores for up to 24 hours, which Reddit's settings article lists as 1,440 minutes. That is separate from contest mode, which scrambles all the comments and hides their scores outright.

Why can't you recreate the Best score table from a live Reddit thread?

Reddit's interface shows one net number per comment, not the separate upvote and downvote counts the Wilson formula needs. The ordering you see is the only output of that formula you get to observe, so the vote split behind it stays hidden.

Is Reddit's current comment ranking algorithm open source?

Reddit's production ranking is closed source today. The Top and Best formulas described here come from reddit-archive/reddit, the codebase Reddit stopped updating in 2017, so they show the last version Reddit published rather than what runs now.

Is a comment's net score the same as its karma?

A comment's net score, upvotes minus downvotes, is separate from the karma total on a user's profile, though the two move together. Net score only ranks that single comment under Top, while karma is the broader profile figure.