Strongly related: How do we deal with octuplicate questions?

This is not a question about how to deal with duplicates, it's a simple "meta" question:

What is the most rampant duplicate on Stack Overflow?

  • The particular duplicate must be "alive" on Stack Overflow (not merged or closed duplicate)
  • The duplicate-ness must be pretty unquestionable.

For example:

This is a duplicate of score 2 1.

They are both so close that it makes little sense to have separate questions.

However, score 2 is pretty uninteresting.

(The rationale of this question is to find the duplicates so we can get the administrators to merge them. It is also to find better ways to find dupes in the first place, and perhaps turn finding duplicates into a game.)

25 Answers 25


How to parse HTML with RegEx?

...by far has the most dupes.

... just to name a few.


I guess it is:

Me no can get program working - you help please code here pls debug. Thxxxx

  • 78
  • 17
    Apparently he/she has an assignment with a deadline :) – Kenan D Jan 12 '11 at 21:17
  • 2
    Four years later, this answer is still a H O O T – Howard Pautz Sep 12 '14 at 5:53
  • 4
    @HowardPautz Six years later, it's still funny. – cat May 16 '16 at 13:53
  • 3
    Don't forget "tanks in advantage" – JAL Dec 3 '16 at 14:22

On Server Fault, it's definitely "How do I host my server from home":

(And that's not even all of them.)

Which is ridiculous because the answer is always "Don't" - and I thought this was a site meant for professionals...

  • 2
    Well, sometimes "don't" is the proper and professional answer... but that's a different discussion for a different time. I would have figured that was a prime target for duplicates, I just never expected that much ... variety ... in the wording. – AnonJr May 17 '10 at 18:23
  • Don't is definitely not the answer, the answer comes in regards to availability guidelines. If you only LIKE to have your site up, be all means host from home. If you NEED your site up. Use a real host. – Chris Marisic Jan 11 '11 at 19:03
  • 1
    What's scary is the same answer applies to "How to parse HTML with RegEx" - again the ideal answer is "Don't" but there are some limited cases where it's possible ;) – Zhaph - Ben Duguid Apr 5 '12 at 9:52
  • 1
    As of today, a search for +host +server +home turns up 1,153 results on SF. Not all of them are this question, but it appears that the vast majority are. – Michael Hampton Oct 4 '12 at 23:36
  • That looks more like a topic than a question archetype. – Simon Kuang May 31 '14 at 5:51

Since Jarrod spent so much time and effort cleansing the data, I figured it'd be a shame not to have some fun with it.

Here are the top 30 questions (by # of questions closed as duplicates of them) on SO:

9363    http://stackoverflow.com/q/218384
4533    http://stackoverflow.com/q/14220321
4070    http://stackoverflow.com/q/4660142
3304    http://stackoverflow.com/q/4261133
2974    http://stackoverflow.com/q/513832
2937    http://stackoverflow.com/q/18050071
2271    http://stackoverflow.com/q/12573816
2240    http://stackoverflow.com/q/2973202
1884    http://stackoverflow.com/q/12769982
1850    http://stackoverflow.com/q/24644436
1745    http://stackoverflow.com/q/588004
1642    http://stackoverflow.com/q/8028957
1398    http://stackoverflow.com/q/203198
1391    http://stackoverflow.com/q/750486
1325    http://stackoverflow.com/q/60174
1259    http://stackoverflow.com/q/11321491
  968    http://stackoverflow.com/q/949433
  906    http://stackoverflow.com/q/495021
  859    http://stackoverflow.com/q/5554734
  855    http://stackoverflow.com/q/279170
  842    http://stackoverflow.com/q/3577641
  810    http://stackoverflow.com/q/20279484
  794    http://stackoverflow.com/q/23667086
  754    http://stackoverflow.com/q/22937618
  745    http://stackoverflow.com/q/17498216
  724    http://stackoverflow.com/q/40480
  703    http://stackoverflow.com/q/13102045
  685    http://stackoverflow.com/q/6343166
  636    http://stackoverflow.com/q/13840429
  628    http://stackoverflow.com/q/15112125

(And yes, I'm counting deleted posts too - lookin' at you, PHP)

select top 30 count(*) as dups, 
  concat('site://q/', RelatedPostId, '|', isnull(q.Title, RelatedPostId)) as Q,
 iif(max(q.ClosedDate) is not null, '*', '') as Closed,
 iif(max(q.DeletionDate) is not null, '*', '') as Deleted

from PostLinks
 join PostsWithDeleted q on q.Id=RelatedPostId

where LinkTypeId=3

group by RelatedPostId, q.Title
order by count(*) desc

This is now available for your use and abuse on the Stack Exchange Data Explorer!

  • The MySQL one would have been my guess for the top-spot... they're a never-ending deluge; and those are just the ones that got closed as dupes of the merged dupes at the top... your query isn't recursive ;-). – ben is uǝq backwards Feb 20 '13 at 8:43
  • The data code appears to be broken. I have posted a new version on my answer: meta.stackexchange.com/a/244636/200117 – Ciro Santilli 新疆改造中心996ICU六四事件 Dec 4 '14 at 14:00
  • I wonder why the top questions among these all involve PHP… :] – balu Oct 16 '17 at 15:46
  • These days, the top one is java, @balu - never a dull moment! – Shog9 Oct 16 '17 at 23:18

One I see often is "How do I center an element vertically and horizontally with CSS?"

  • 17
    The worst part is this question has like 8500 answers all of which work in some ways and don't work in others. – Chris Marisic Jan 11 '11 at 19:04

Attempting to modify a C string results in an access violation:

This must come up once a week.

  • 3
    If not more .... – Tim Post Jul 20 '10 at 10:44

I have a 3 pointer:

Any decent C# profilers out there? Best .NET memory and performance profiler? What Are Some Good .NET Profilers?

Really they should all be folded into a single mega community wiki .... There is no value in having the 3 questions.

  • Agreed, they should probably be merged. 3 points for you :) – Jonik Aug 3 '09 at 20:36
  • 2
    nobody asking for an indecent profiler? – Thorbjørn Ravn Andersen Jun 4 '11 at 11:23


That's a duplicate score too high to count.

  • 1
    Eric, there is no clear unambiguous list for the moderator to work with. See how Marc was able to resolve the dupe I posted in seconds. Surely you could beat my measly score of 2. – waffles Jul 26 '09 at 14:30

"foreach captured variable c#"

Jon kindly listed some of them here... and that was just in November; it will be longer now...

The problem with this language gotcha is that until you understand what is happening, you can't know what to look for... IMO, this is one of the good use-cases for tag-specific home pages, where we can (manually) add a FAQ for that tag (i.e. link to the canonical answer).


Data query tested in 2016

Shog9's Data Explorer query didn't seem to work for me, so I crafted one that did: http://data.stackexchange.com/stackoverflow/query/254033/rampant-duplicates-questions-with-the-most-duplicates

  l.RelatedPostId AS [Post Link],
  COUNT(l.PostId) AS DupCount
  PostLinks l
  l.LinkTypeId = 3
  DupCount DESC

This is quite "rampant": Best Java 7 features

Pretty much exact duplicate of What new features in java 7 do you find most useful? (posted 9 months earlier), very close to What are you looking forward to in Java 7? (6 months earlier), and somewhat close to many others.

What also springs to mind are the countless variations on the theme "What is the best Python (web) framework?", with ever so subtle differences in emphasis and formulation. (Right now I'm not delving too deep into those, but take a look at python+frameworks, python+framework and python+web-frameworks.)


Android has some serious flaws in its touch event model, and this has caused many people to ask how to fix the problem (the real answer seems to be "upgrade to Gingerbread", sadly):

I've marked most of these of dupes of the original, not sure if merging or what is the solution here. The bug report mentioned in 4342464 is the most correct answer IME.


Concatenate row values into a single column is fairly common for SQL Server


  • Can you create a list of actual merge candidates, so I can score it :p – waffles Jul 27 '09 at 8:38

In the past:

[Why/When] Should I use xxxx Programming Language?


I'm interested in Java, but every Java regular expression question I see seems to be "plz send me teh regex".


I feel like mod_rewrite should be on this list but I'm too lazy to go look up a lot of duplicates. I'll mark it CW and someone who's motivated (or tomorrow when I'm bored I) can go look some up.

  • Haven't got bored yet? :P – Trufa Jan 30 '11 at 21:51
  • @trufa haha, totally forgot about it. Now you've reminded me ;) – jcolebrand Jan 31 '11 at 13:52
  • @drachenstern hehe no worries but don't dare look at me, I'm the laziest bastard you will ever encounter :) – Trufa Jan 31 '11 at 14:58
  • @trufa ~ My motto is that all programmers should be lazy. But not too lazy. (mainly in re: functions and reuse, etc. Copy-paste twice, but after that make a function and quit copy-pasting, too much effort to do so, making a function makes you lazier ... blah blah TL;DR ;] ) – jcolebrand Jan 31 '11 at 15:30
  • @drachenstern codinghorror.com/blog/2005/08/… – Trufa Jan 31 '11 at 15:55
  • @trufa ~ SEEEEEE!!!! ;) :D – jcolebrand Jan 31 '11 at 16:17

I'm pretty sure the one I encounter the most is along the lines of "How come .1 + .1 + .1 doesn't equal .3?".


Anything where the answer is dos2unix. The symptoms are varied and the clue quotient of the OPs is mostly, shall we say, chequered. In the end, by the time it's solved, it's obviously off-topic for SO, but you see some good programming and debugging coaching in the speculations leading up to that.

The examples I am finding are less spectacular than the best I've seen. These all contain literally dos2unix in the answer, but there will be hundreds more with different wording.


Having voted to close more than 1600 questions, and succeeding in many of them, these are the two I found (anecdotal) most annoying (in number, yes) from C#/.NET world:

  1. Get property name and type using lambda expression

  2. And even more duplicated is this: Conditional operator assignment with Nullable<value> types?

  3. And even more: Pass An Instantiated System.Type as a Type Parameter for a Generic Class

That's just from my experience. The language designers can take a cue to find the most requested feature..

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