Created attachment 107571 [details] generated JSON string To reproduce a problem, open a file with some JSON content having couple of hundreds of KBs in size. After removing the limitation for the number of shown characters, kate becomes unusable. Navigation, scrolling, etc. is hardly possible and the CPU consumption is very high. It's not even possible to work with a 500kB file on a machine with 12 cores. Attached is an example file (generated with json-generator.com) causing such problems. Visual Studio Code for example doesn't have any performance issues with such files.
*** This bug has been marked as a duplicate of bug 345775 ***