I create and upload quite a bit of video content. I'm just curious what people's experience is with clip length. Is there an optimum clip length that buyer are looking for, or does it even matter? What's your experience?

I rarely submit anything shorter than 10 sec, nor longer than 30 sec.  10-20 sec is my "sweet spot."

Note that most agencies will not accept anything less than 5 sec (yes, I know one that accepts 3 sec, but... really??), nor longer than 60 sec.

My clips are almost entirely 4K unless slo-mo, which are HD (limit of my recording hardware).

More specifically I was wondering if there was any advantage to submitting longer clips. I realize that short clips (under 5 seconds) have very limited use. I seem to sell mostly between 10 and 25 second clips, but I wasn't sure what other people's experience was.

The owner of BlackBox, and a few of his most experienced people, have been doing stock video for more than a decade. Their experience is that the prime length is 10 to 15 seconds.  I tend to push that to 20 sec, so the buyer has a bit of flexibility.

They state that if your clip is longer, you are best to break it into 2 (or more) clips and post each separately.

When I look at videos in which I know (or suspect) that stock footage is used, I keep a mental stopwatch on the likely stock clips.  Yep, it is very rare for one to last 10 seconds.  3 to 5 seems far more common for those kinds of clips.  BB did point out one specific video that was made entirely with stock clips last year.  When I watched it, I never saw a scene go longer than 5 seconds.

BTW, I am not advocating BlackBox. Merely noting that the owner does appear to be an experienced and successful stock video producer, and passing along things he has said, and which seem to make sense to me (after watching published videos more closely).

duplicate

It depends on the clip.  I have some that are 6 seconds and some that are 20.  My 6 second clip has sold a couple of times for $400.  The idea behind the 20 second clips is that buyers can take snippets from that clip that fit their needs.  But if the clip is really unique, bigger is not always better.  Like many here, I have learned to upload 10 sec or less in most cases, but sometimes (not often) more if I think it is needed.

It depends on the clip.  I have some that are 6 seconds and some that are 20.  My 6 second clip has sold a couple of times for $400.  The idea behind the 20 second clips is that buyers can take snippets from that clip that fit their needs.  But if the clip is really unique, bigger is not always better.  Like many here, I have learned to upload 10 sec or less in most cases, but sometimes (not often) more if I think it is needed.

What type of material are you shooting? I suspect that makes a difference as well.