A THUMBDATA4-1967290299 file is a data file created by the Gallery app included with select Android phones, such as Sony Xperia and Samsung J7. It contains indexed properties about every thumbnail image stored in the Gallery app to help it load thumbnail images quicker.

The THUMBDATA4-1967290299 file is created by the Gallery app on the phone to cache information about images that have been indexed. Caching the indexed images helps the Gallery app load images quicker and reduce lag time when displaying thumbnails. The more images you have in the Gallery app, the larger the THUMBDATA4-1967290299 file grows. It may become several hundred MBs, or in some cases, several GBs in size if you have a large number of thumbnail images in your Gallery app. The file increases in size every time a new image is added. Even when an image is deleted, the indexed properties of the image still remain in the file. You can use an Android file manager to navigate to your thumbnail index files, which are located in the sdcard/DCIM/.thumbnails directory. The THUMBDATA4-1967290299 file is typically stored with the .THUMBDATA4-1763508120, .THUMBDATA3-1967290299, and .THUMBDATA3-1763508120 files. To reduce the THUMBDATA4-1967290299 file size, remove images from the Gallery app then delete the THUMBDATA4-1967290299 file. The file will be regenerated by the Gallery app but only for the images stored in the app. If you do not want to remove images from your device, delete the THUMBDATA4-1967290299 file and create a new file in the same .thumbnails folder using a file explorer, such as ES File Explorer. Then, name the file .thumbdata4-1967290299. This will stop the re-creation of the THUMBDATA4-1967290299 file.