Using app and appears to work great. Photo library memory used is shrinking however the video slimmer app is growing by the amount the original video has reduced. Just seems to be swilling around what's already in the memory . Taken from one place and put somewhere else ???
Like any other video converters, the video slimmer app will have some temporary files created in the daily use which you need to clear from time to time to save iPhone space. You can export the compressed videos from the slimmer app to your photo library / camera roll, then delete these temporary files from the converted videos panel. You can tap on the Converted Video, swipe from left to right, you will see a red delete button, tap on it to delete a converted video. Alternatively you can also tap on the share button on the top right corner to delete the selected video or simply choose delete all to clear all converted videos from the slimmer app.