The instinct is understandable: it is your work and people take it. But a watermark does not stop anyone determined, and it puts a small piece of noise on every photo for the people who were never going to steal it.
When it does nothing
Reposts with credit — the mark is redundant. Theft by cropping — the mark is gone. Screenshots for a mood board — nobody reads it. In most feeds it is a signature on a letter nobody is forging.
The two cases for it
- Work that is routinely lifted and resold: stock-style imagery, patterns, designs that are the product. A small mark in a corner people would have to crop awkwardly.
- Reach without attribution: if your photos travel far and your name does not, a quiet handle in the corner is how someone finds you three shares later.
If you do it
Small, low contrast, one corner, the same every time. Your handle, not your logo. Applied automatically so you never forget and never do it by hand.
The best protection is still the boring one: post at a resolution that looks good in the feed and is useless for print.