title screen demos.

GZDoom will only play back demos recorded in the same version of GZDoom, so you can record your own using GZDoom itself, but as soon as a new version of GZDoom comes out the demo will be broken, and given how often the port updates, it's sadly probably not worth it as your demo will be broken in just a few months.

Vanilla demos will still work in vanilla, which will be the same standard til the end of time, but even then they only play back in vanilla-compat ports. Sadly the title screen demos are pretty much ALWAYS ignored in modern wads due to all this..

1 minute ago, Doomkid said:

but as soon as a new version of GZDoom comes out the demo will be broken

im making a iwad/standalone game. and im not updating the source port.  so if i record a demo. it will appear on screen?

That’s right, as long as it’s being played in the same version of the same port it was recorded in, it will work.

@Doomkid did it did not play on title screem. it also was an unknown file in slade 3.

GZDoom may not even have demo playback at all in that case, though I thought it did.

1 hour ago, Tuckymonster said:

@Doomkid did it did not play on title screem. it also was an unknown file in slade 3.

You might be interested in reading up on recording demos.

These WIKI entries have the definitive answers.

https://zdoom.org/wiki/Demo

https://zdoom.org/wiki/Command_line_parameters

3 hours ago, Doomkid said:

GZDoom may not even have demo playback at all in that case, though I thought it did.

In all the years Ive played GZDoom I've never seen it start or play a demo while waiting...

From the Demo page of the Zdoom Wiki:

Quote

ZDoom is also not compatible with the vanilla Doom demo format and will therefore not play the demo loop from the various supported IWADs. Because of the lack of backward demo compatibility, it is not advised to put built-in demo lumps in a ZDoom mod, as they risk getting obsoleted. Instead, a scripted TITLEMAP can be used.