Concretely, the mark is composited onto the decoded image and the result is re-encoded once, so add the watermark last, after any resizing or compression, rather than watermarking a master you will process again. You control the position, the size and the opacity, and the same settings are applied consistently across everything you upload.
Can I use my own logo, or only text?
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Either. Upload a transparent PNG logo, or type text and choose the font, colour and opacity. A tiled repeat is available when one corner mark is too easy to crop away.
Does the file format affect how the watermark comes out?
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It does. JFIF is a plain JPEG bitstream under the original 1992 interchange header, which is why some viewers show it as a generic image and cameras still emit it. That governs how cleanly a semi-transparent mark can be blended into the underlying content.
Anything specific to JFIF worth knowing?
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Yes — many editors silently rewrite a JFIF as an ordinary JPEG on save, so keep the original if the .jfif extension itself matters to whatever consumes the file. It affects when in your workflow the mark should be applied.
Does a watermark actually protect my work?
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It deters casual reuse and it credits you; it is not security. A corner mark can be cropped and a faint one can be painted out. If protection matters, a large semi-transparent mark across the subject is far harder to remove than a discreet one in a corner.
Should I watermark before or after resizing?
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After. Watermark the final deliverable at its final size, so the mark stays legible and proportionate. Watermarking a master you will process again means the mark gets resampled and compressed along with everything else.
