Privacy
IMG_4021.HEIC says more than it looks like
Default filenames encode device conventions and sequence, and a service that keeps original names keeps a small identifier you did not think about.
Guides on Privacy: Who could see it, how, and what each path costs to close, Soft delete, backups, caches and logs, Sometimes, and the policy clause that says so is easy to miss
Yes, a filename is metadata, even though it sits outside the file rather than inside it. It is information a device wrote for you rather than information you chose, and stripping every field inside a photo does nothing to a name that travels alongside it.
What the pattern reveals
IMG_4021.HEIC and PXL_20260814_193022.jpg are both conventions, not accidents.
The numbered pattern comes from the camera file-system rules (DCF) that the Camera & Imaging Products Association maintains with Japan's electronics industry body JEITA, which build a file name from four free characters and a four-digit file number.
An iPhone's IMG_#### counter follows that shape and identifies the device's own running sequence - two photos numbered close together were very likely taken close together in time, on the same device, even with all internal metadata removed.
A Pixel's PXL_YYYYMMDD_HHMMSS pattern is more direct still: it puts the capture timestamp in the name itself, in the clear, independent of anything EXIF carries.
Android manufacturers vary in their own conventions, and some embed a device model abbreviation directly.
None of this is deliberately identifying - it is just a device doing what device software has always done, generating a unique name without thinking about who might see it.
Why it matters more than it looks
A single filename tells a stranger very little. A set of filenames, kept in sequence across multiple uploads to the same service, tells a different story: which photos came from the same device, roughly when, and in what order relative to each other - all without opening any of the files. This is a smaller exposure than GPS coordinates, but it is a persistent one, because renaming is a step most people never think to take, and most upload flows do not rename for you.
What to do about it
Rename before uploading, to anything - a generic string, a random one, or simply the service's own name if it offers to assign one on save. This is a smaller step than stripping EXIF, and it addresses a different channel entirely; doing one does not do the other, and neither substitutes for reading what a file actually contains before you send it. Some services rename files on ingest as a side effect of storage, which incidentally handles this for you - worth checking, but not worth assuming.
Where this fits among the rest
None of it touches how an image is scored - a model never sees a filename, only pixels. It is purely a question of what an upload discloses beyond the picture, the same category as the GPS field or the software tag in a text chunk, just outside the file rather than in it. Comparison-minded users tracking their own submissions over time have a reason to think about naming consistency for a different purpose entirely - Penis Rater's notes on preparing a submission cover that from the tracking side, not the privacy one. A file sent to a human judge carries its name along too, and what belongs in that kind of submission is a related but separate question of etiquette rather than exposure. It has no bearing at all on a measurement taken with a tape, which Measure My Cock's method never turns into a file in the first place.