Exif is information data set to an image file when you take photos with cameras.
GPS data like latitude and longitude are often included in Exif data, so you have to be careful when uploading photos you took to public spaces on the Internet.
Popular photo sharing services like Instagram automatically remove GPS data when photos are uploaded, but if you're not sure how GPS data are treated on other services, you may want to check and remove Exif data by yourself before uploading.
There are many tools to check and edit Exif data, like ExifTool. And for programmers, most popular programming languages have some kind of libraries to treat Exif data.
For Javascript, Piexifjs would by easy to use. It works both for web client-side and Node.js.
Here is a sample script to show Exif data of JPEG images:
And Here is a sample to remove Exif data from JPEG images:
