Can I change the internal resolution?

I'm almost done with my Construct 2 game. I set the project screen to 1080x1920 and have the assets resolution accordingly. I simply assumed resolution could be adjusted for each device. I'm now testing the game on mobile and segments with many objects on screen are having slow downs.

Is there a way to manually change the resolution the game is rendered in order to improve performance? Like, what if I set the canvas size to 720x1280 and layout scale to 0.6666? Would that make the game lighter? I really hope this can be done without major changes to the game.

First off, I recommend you confirm that resolution is actually the culprit of low fps before you ask the wrong question, or spend a lot of effort fixing it when it wasn't the problem to begin with.

Besides that, that's not exactly how resolution and performance is related. No matter what resolution your sprites are, the device still has to up/downscale them and draw as many actual pixels as it needs to fill up the screen.

What does matter is memory use - your source images will be loaded into memory at their original resolution no matter what the device up or downscales them to after. This can cause issues if your total memory use goes over the available VRAM on the user's device. So to lower your VRAM use, you would need to change the sprites in your project use lower resolution textures/images.

However, do note again that if slowdowns only occur when a lot of objects are on screen, I find it unlikely that texture resolution is your problem. See construct.net/en/make-games/manuals/construct-3/tips-and-guides/performance-tips and construct.net/en/blogs/construct-official-blog-1/optimisation-dont-waste-time-768 for more information.

Depending on your definition of "many objects" and the capabilities of your target device, you might simply just have to reduce the number of objects on screen at any given time. There are tools to help measure this if you search "Performance" in the examples browser.

First off, I recommend you confirm that resolution is actually the culprit of low fps before you ask the wrong question, or spend a lot of effort fixing it when it wasn't the problem to begin with.

Besides that, that's not exactly how resolution and performance is related. No matter what resolution your sprites are, the device still has to up/downscale them and draw as many actual pixels as it needs to fill up the screen.

What does matter is memory use - your source images will be loaded into memory at their original resolution no matter what the device up or downscales them to after. This can cause issues if your total memory use goes over the available VRAM on the user's device. So to lower your VRAM use, you would need to change the sprites in your project use lower resolution textures/images.

However, do note again that if slowdowns only occur when a lot of objects are on screen, I find it unlikely that texture resolution is your problem. See construct.net/en/make-games/manuals/construct-3/tips-and-guides/performance-tips and construct.net/en/blogs/construct-official-blog-1/optimisation-dont-waste-time-768 for more information.

Depending on your definition of "many objects" and the capabilities of your target device, you might simply just have to reduce the number of objects on screen at any given time. There are tools to help measure this if you search "Performance" in the examples browser.

I'm aware of the potential improvements of less objects on screen but is the internal resolution fixed? I made the game around the 1080p resolution so that devices with those screens could run it without stretching things up. I also assumed it would be easy to set different resolution modes so weaker devices could run it.

Try setting fullscreen quality to low and seeing if it makes a difference.