How to erase data from android?

[sdhfg]

I am going to selling my old phone , but the phone store some importan data or personal information , i am afraid of these deleted data appear on the phone again , who have any good idear to solve this issues , thanks!

[Emichael]

Actually, you can erase all the data by factory reset. But some people said that the data is just marked as invisible but still exist in the database. If you want to totally wipe all your data permanently, you can try to use the FORecovery Data Eraser for help. Another method is to use your camera to take a long long long video until the internal storage is full, then delete it. But before taking the video, you need to factory reset your phone to get the double security insurance.