Very concise list of great resources 
Ive recently upgraded to coco3.10 and it was scaling down all my images unlike in previous versions. I just commented all code related to director->setContentScaleFactor to disable that at AppDelegate.
@erebar
Most probably because of much higher resolution of your device on which you ran the game.
Design resolution only tell that according to which device’s resolution you designed your game art.
However, scaling up/down depends upon what resolution policy your used OR what kResolution you used.
I would recommend posting code before asking such questions! 
Thanks for the reply, the problem was all that code related to setContentScaleFactor and smallResolutionSize, mediumResolutionSize and largeResolutionSize. This wasnt there on older versions of cocos2dx. I mostly use just 1 set of images for all devices.
Wow! Never thought this existed! It was always soo exhausting to get all possible resolutions supported when i was programming in codea!
Existence of what? Design resolution policies in Cocos or this thread! You can search for 2-3 more threads on similar topic on this forum. All filled with knowledge on design res 
hii… I’m new to C++ as well as Cocos2d-x also… I was developed one Tic Tac Toe game for iPhoneSE. but, the Positions are changed while running the game in iPad. so, how can I set the perfect resolutions for all devices?