Hi and welcome,
You won’t get many replies to a question that vague which is lacking somewhat in important information I’m afraid.
Some questions.
- What is your operating system and version of Shotcut?
- Do you mean the exported video is a smaller file size, or it is smaller in dimensions (resolution) than the original input video? At this moment I assume the latter.
- What is the resolution of the original input video. Is it 1280x720, 1920x1080 or perhaps 4k?
- What is your video mode set to?
When exporting, on the export tab tick the advanced box and then look at the resolution of the output video. Those numbers shouldn’t need adjusting but they should also match your input video. If they don’t then you have probably selected the wrong video mode (see above).
That’s probably enough info to get the ball rolling. Good luck!