On a Pixel, open Settings → Storage. On a Galaxy, open Settings → Device care → Storage. Start with the largest category and remove downloads you can get again. Check that photos or other files are backed up before removing the copies on your phone.
01Check what is actually full
Section linkLook at the categories on the Storage screen. If apps take most of the space, deleting a few screenshots will barely help. If only your Google Account is full, freeing phone storage will not increase your account quota. Some Galaxy versions use the name Battery and device care; search Settings for Storage if the path differs.
02Remove downloads where you got them
Section linkCheck the Downloads folder in your file app, then look inside streaming, podcast or map apps for offline content. Use the app’s own download controls for those files. Copy personal videos or documents you want to keep to a computer, open the copies to verify them, then remove the originals from your phone if you have a separate backup.
03Clear cache for a large app if needed
Section linkIn Settings → Apps, pick the app. On Pixel, open Storage & cache; on Galaxy, open Storage. Clear cache removes temporary files that can build up again. Clear storage on Pixel or Clear data on Galaxy resets app data and can remove local files, progress or settings. Leave that option alone unless you know how to recover what you need.
04Keep backed-up photos and remove device copies
Section linkIn Google Photos, confirm the backup on the correct account and open a few of the files you plan to keep from a browser. Then tap your profile picture → Free up space on this device and review the amount shown before confirming. This removes eligible local copies; you can still view the backed-up versions in Google Photos when online. Do not use the ordinary Delete action for this purpose. Recheck Settings → Storage after cleanup.