Add a Watermark to Images

The first is the familiar one. When you post photos you took or artwork you made to a blog, a portfolio or a shop, a watermark keeps your name attached. If someone reposts the image, the credit travels with it.

The second is less talked about but just as practical: marking copies of IDs, bank statements or contracts with their purpose before submitting them — something like "For ACME Bank verification only — 2026-08-06" written across the scan. Banks, landlords, carriers and sign-up processes routinely ask for a copy of your ID, and once a copy leaves your hands you have no idea where that file travels. Writing the recipient and the date on the copy makes it obvious if that exact file ever resurfaces somewhere it shouldn't.

To be clear, this is not a legal guarantee of anything — it is a practical precaution. It makes the copy awkward to reuse for any other purpose, and if something does go wrong later, the marking hints at which channel the copy leaked through. Some recipients only accept clean copies, so check first that a marked copy is acceptable.

A small watermark tucked into a corner is practically no watermark at all — a light crop removes it completely. If you actually want to deter unauthorized use, run the text across the subject itself, or use the tile layout above to blanket the whole frame. A watermark only means something when removing it requires damaging the image.

That said, no watermark is bulletproof. Modern eraser tools and generative fill can remove watermarks convincingly, especially on photos with simple backgrounds. The realistic goal is not "prevent" but "inconvenience": casual repost-and-run users give up, and anyone determined enough at least has to spend real time on it.

Document copies are a slightly different game. There the text is meant to be read, not hidden, so keep it clear of faces and photos and let it lightly overlap printed details like names and numbers. Cover the information so heavily that it can't be read, though, and the recipient will reject the copy.

Too dark and the watermark ruins the photo; too faint and it means nothing. Start around 40% and nudge it up or down against the preview. For photos meant to be enjoyed, 20–30% is enough; for a purpose notice on a document copy, 50–60% keeps it unmistakably legible.

Color depends on the background: white text drowns in bright photos and black text drowns in dark ones. That is what Add outline is for — a thin contrasting border around the letters keeps them readable on either. When batch-processing a mixed set of photos with different brightness, leaving it on is the safe move.

Size is set not in pixels but as a percentage of the image's longer side. The same pixel size that vanishes on a 4,000-pixel photo would smother an 800-pixel one; a percentage keeps the watermark proportionally similar across a folder of mismatched sizes.

Because this tool routinely handles things like ID copies and contracts, this point matters most. From the moment you pick an image to the moment you save, every step happens inside your browser and no file is sent to any server. Even the watermark drawing uses the browser's built-in canvas — nothing goes out over the network.

Nothing is recorded either. The images you choose and the text you type are never written to browser storage, so closing the page leaves nothing behind. Making a quick marked copy on a shared computer is fine — just close the tab when you are done. The flip side: refresh the page and you start from scratch.

The watermark comes out too big or too small

The size is measured against the longer side. On a landscape photo, 5% means 5% of the width — but on a portrait photo it means 5% of the height, which looks large relative to the narrow width. With a mix of orientations, click a portrait thumbnail to preview it before settling on a size. Clicking any thumbnail switches the preview to that image.

The text edges look dirty after saving as JPG

JPG compression shows most around sharp edges, which is exactly what text is — hence the smudgy halo around the letters. Raise the quality to 95 or higher, or save as PNG and it disappears. PNG makes photos several times larger, though, so if file size matters, try just raising the JPG quality first.

My transparent PNG logo shows up as a solid box

Usually the logo file is not actually transparent. A PNG with a filled white background stamps that white rectangle onto the photo, and on dark photos the logo itself may disappear instead. Open the file in an image viewer: if the background shows a gray checkerboard, it is transparent. If not, run it through a background-removal tool first.

Processing many images is slow

Everything happens in your browser, and at full original resolution. A 4,000-pixel photo means tens of millions of pixels redrawn per image. To avoid running out of memory the tool processes one image at a time and releases each from memory as it finishes. Batches of 10–20 at a time run more reliably than dumping in dozens at once.

Is the saved image a different size from my original?

No — it is identical. Only the on-screen preview is scaled down for convenience; the saved file keeps the full original resolution. If you want smaller files, run them through an image compressor separately afterwards.