pfSense

The diag_packet_capture.php p[age will try to display any size of pcap when the capture is stopped regardless of how large it is.

This can result it either long load times and an unmanageably large page or at larger sizes it exhausts the available php memory for a single page:

Crash report begins.  Anonymous machine information:

amd64
11.2-RELEASE-p4
FreeBSD 11.2-RELEASE-p4 #2 b00c407ba5d(RELENG_2_4_4): Mon Nov 26 11:41:48 EST 2018     root@buildbot2.nyi.netgate.com:/build/ce-crossbuild-244/obj/amd64/ZfGpH5cd/build/ce-crossbuild-244/pfSense/tmp/FreeBSD-src/sys/pfSense

Crash report details:

PHP Errors:
[27-Dec-2018 19:35:43 America/Toronto] PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 532692992 bytes) in /usr/local/www/diag_packet_capture.php on line 541
[27-Dec-2018 19:35:43 America/Toronto] PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 532676888 bytes) in Unknown on line 0

No FreeBSD crash data found.

However it is still possible to download the capture when this happens.

It would be nice to see it show just a message explaining why it's not showing the capture. Or maybe a new detail level of 'None' so you have to deliberately choose 'Normal' to attempt to display it. That could apply to any capture over, for example, 5000 packets.