Exported file size anomaly.

Hello! New here so hopefully I won't make a pigs ear of my query....

I'm having a problem with FCPX telling me that my exported files are going to be one size and then finding that the size given is wildly inaccurate. To explain...

If I export my file via File -> Share -> Export File... and then select 'Computer' as the Format it will give an expected file size in the bottom right corner of the dialogue box, in this instance 87.1Mb:


The file exported is actually slightly larger but it is nonetheless fairly accurate - 91.6Mb.



If, however, I select 'Web Hosting' the expected file size upon exporting is shown as being 147Mb...


....however the file actually exported is much smaller - 44.1Mb.



Can anyone please explain why this is happening / what it is I am doing wrong? Cheers.

Is there anything wrong with the exported files playing back?

The share window shows an estimated file size prior to compression/export. It is not intended to be exact, although it's usually close. Your first example appears normal (estimated 87MB, actual 91MB). The second example is further off, but maybe the multi pass encoding was more efficient than estimated. If the files play fine and look fine, I don't think there is any problem.

No problems with either file, they play back fine.
I made the query as I was expecting the 'Web Hosting' file to be larger than the 'Computer' file regardless and it also struck me that the difference in the 'estimated' and the 'actual' sizes were inordinately large but it appears from what you say that there's nothing to worry about. Result!

Many thanks for the prompt and helpful replies, it is appreciated.

Web files should be the smallest. There is progressive download buffering (very little actually "streams", contrary to popular belief). There are bandwidth issues. It has to be as small as possible to play well. Usually suffers some sort of quality/fidelity degradation issue of some sort.

Playing from a hard drive directly (computer) can be much larger with more quality and more efficient playback.