I just made a 3 hour long video and it’s almost at 4GB. I want it to be 1080p. That resolution is good enough for me. What settings for exporting video is good? Im doing .mp4 file format.
The Shotcut FAQ recommends the H.264 High Profile preset for exactly this case - 1080p MP4 for sharing. At 4 GB for a three-hour video you are already at roughly 3 Mbit/s, while YouTube’s own upload recommendation for 1080p is 8 Mbps, so your file is already on the lean side. If you still want it smaller, the Quality slider in the export Codec tab controls the H.264 quality level - lower it a few steps and export a short section to judge. Going to 720p would be the bigger lever, but since 1080p is your target I would keep the preset and accept around 4 GB.
AVC (H.264) is great in that it’s widely supported - it’s a couple of decades old so by this point virtually any device or program that can play videos supports it. But newer codecs like HEVC (H.265) and AV1 offer better compression, so if your audience has modern devices/programs, using one of those will yield smaller file sizes for the same visual quality.
Your file is at about 3 mbps bitrate, if your video is mostly static (so maybe a lecture, a powerpoint or a selfie-style with a person talking) you could probably get it even lower.
Use a ranged marker to only export a 1 minute test and use the HEVC main profile preset with quality at 42% (crf30), I got good results with this combination but beware, it will take long to export - this is why I recommend 1 minute test to see if you are find with waiting for the whole 3 hour export.