Yes. Deleting these files will not harm your photos; it only removes the cache. How to stop them from growing:
If you delete them, Android will simply recreate them the next time you open your Gallery. Forensics: thumbdata viewer free
If you must use a dedicated viewer, run it inside a (like Windows Sandbox or a throwaway VM) and never upload your thumbdata files to an online “free viewer” — that’s an instant privacy disaster. Forensics: If you must use a dedicated viewer,
Since thumbdata files are collections of JPEGs, you can use a free hex editor (like HxD for Windows) to find the FF D8 FF headers that signify the start of a JPEG image and manually extract them [2, 5]. thumbdata viewer free
termux-setup-storage cp /sdcard/DCIM/.thumbnails/thumbdata4-- ~/storage/downloads/ # Then copy to PC and use binwalk or Thumbdata Reader.