A photo file is two things, and only one of them is the picture
Alongside the image data, most photographs carry a block of information about how and where they were taken. It is called EXIF, it is invisible when you look at the picture, and it travels with the file wherever it goes.
The camera model, the exposure settings and the timestamp are harmless enough. The boxed line is the one that matters: on most phones, by default, a photograph records where it was taken, to within a few metres.
Useful while it stays yours, a problem the moment it leaves
Location data in your own photo library is a feature. It is what lets a phone group a holiday, put pictures on a map, and find the ones from a particular day.
It becomes something else entirely when a file goes out. A photo taken in your own garden carries the coordinates of your garden. A picture of a bike or a tool posted for sale carries the address of the shed it lives in. A photograph sent to show somebody a job carries the client's address whether or not you meant to share it.
You cannot tell whether a service stripped it
Some platforms remove metadata when you upload. Some do not. The behaviour differs between services, between the app and the website of the same service, and between posting an image and sending it as a file. It also changes without announcement.
Since there is no way to check what happened once the file has gone, the only workable assumption is that the metadata is still attached unless you removed it yourself first.
Blurring the picture does not touch the metadata
This is the gap worth closing, because the two jobs feel like one and are not.
Blurring a face or a number plate edits the picture. The metadata block sits alongside it, untouched, still holding the coordinates. A photograph can have a perfectly blurred plate and still tell anyone who looks exactly which driveway the car was on, which is considerably more revealing than the plate was.
Anything being published for privacy reasons needs both doing, and blurring is the half people remember.
The sideways photo mystery, explained
Orientation lives in the metadata too. A phone generally saves the image the way the sensor read it and adds a flag saying rotate this by ninety degrees.
Software that reads the flag shows the photo correctly. Software that ignores it shows the same file on its side. Nothing is corrupted and nothing needs fixing in the picture, which is why the same image can look right in one app and wrong in the next.
How it gets removed, including here
Metadata does not survive the image being redrawn. Any tool that opens the picture and writes out fresh pixels produces a file with none of the original block attached.
That happens on this site as a side effect of how the tools work. Everything runs in your browser on a canvas, so resizing, compressing or cropping an image here hands back a file with the metadata gone and the orientation already applied to the pixels, so it cannot come out sideways somewhere else either.
If the reason you are here is privacy rather than file size, do the other half as well: blurring a face or a number plate covers why a light blur can be reversed and why the face is rarely the only thing giving somebody away.
Common questions
What is actually stored in EXIF data?
More than people expect. The camera or phone model, the lens, the exposure settings, the date and time to the second, the orientation the camera was held at, and on most phones the GPS coordinates of where the picture was taken. Some cameras add a serial number. None of it is visible in the image itself, and all of it travels with the file when you send it.
Does my phone really record my location in photos?
By default on most phones, yes, and to a precision of a few metres. That is genuinely useful while the photos stay yours, because it is what lets a photo library show you a map of a holiday. It becomes a problem the moment a file leaves, since a photo taken in your own garden carries the coordinates of your garden, and a photo of something for sale carries the address of where it is kept.
Do social networks strip it out?
Some do, some do not, and you cannot tell from the outside. Behaviour differs between services, between apps and website versions of the same service, and between posting an image and sending it as a file attachment. It also changes without any announcement. Because there is no way to check what happened after the fact, the only safe working assumption is that the metadata is still attached unless you removed it yourself.
If I blur a face or a number plate, is the photo safe?
Not necessarily, because you have edited the picture and not the metadata. They are separate parts of the same file. A photo can have a perfectly blurred number plate and still carry the coordinates of the driveway the car was parked on, which gives away rather more than the plate would have. Anything being published for privacy reasons needs both jobs doing, and the blurring is the one people remember.
Why do some photos come out sideways?
Because orientation is stored in the metadata rather than in the pixels. A phone usually saves the image the way the sensor read it and adds a flag saying rotate this by ninety degrees. Software that reads the flag shows it correctly and software that ignores it shows it on its side. That is why the same file can look right in one app and wrong in another without anything being corrupted.
How do I remove it?
Re-encoding the image is the simplest way, because the metadata does not survive being redrawn. Any tool that opens the picture and saves out new pixels produces a file with none of the original block attached. The tools on this site work that way as a consequence of running in your browser on a canvas, so resizing, compressing or cropping here gives you back an image with the metadata gone and the orientation already applied.