Bulk Image Watermark

How to watermark images in bulk

1. Add your images. Drop up to 200 JPG, PNG, WebP, BMP, GIF or AVIF files onto the box above, or choose them from your computer. They stay on your machine.
2. Set up the mark. Type your text or choose a logo, then pick one of the nine positions. The preview shows the first image exactly as it will come out.
3. Watermark and download. Take the images one at a time, or download the whole batch as a ZIP.

Why sizes are percentages, not pixels

A watermark set to 48 pixels is a caption on a phone snapshot and a hairline on a 40-megapixel photograph. Since a batch is rarely all one size, a fixed pixel size is wrong for most of it — so both the text size and the logo size here are a share of each image's own width. Six percent looks like six percent whether the image is 300 pixels wide or 6000.

That is also what makes the preview trustworthy. Because every measurement scales with the image, a preview drawn at a fraction of full size is a true picture of the result rather than an impression of it — and it is drawn by the same function that draws the real thing.

The nine positions

Corners, edge centres and the middle. Each one is inset from the edge by three percent of the image's shorter side, so the gap looks the same on a panorama as on a portrait. Whatever you choose, the mark is kept inside the picture: the clamp is applied to the area a rotated watermark actually sweeps out, so a mark turned 45° cannot poke a corner over the edge, and one larger than the image is centred rather than pushed off one side.

• Top left
• Top centre
• Top right
• Centre left
• Centre
• Centre right
• Bottom left
• Bottom centre
• Bottom right

Formats and transparency

Every image comes out in the format it went in as. Watermarking is a change to the picture, and quietly turning a PNG into a JPG while doing it would throw away transparency nobody agreed to lose. A transparent PNG or WebP keeps its alpha channel, and a transparent logo composites onto the photo rather than arriving in a white box. A JPEG is given a white background before anything is drawn, because JPEG has no transparency at all. If you do want a different format afterwards, the bulk image converter does that on its own.

What the tool refuses to do

An empty text, a missing logo or an opacity of zero will not run. Each of those would produce a batch of files that had been re-encoded and had nothing drawn on them, handed back with a message saying they were watermarked — which is the kind of thing people discover after they have deleted the originals. The button stays disabled and says which setting is the problem instead.

Corrupt files fail on their own. One unreadable image in a batch of two hundred records its own error and the other hundred and ninety-nine still finish, and the ZIP holds only the images that actually worked.

Why watermark in the browser?

Drawing text or a logo onto an image is arithmetic on pixels your computer already has. Sending a file to a server to have that done, then sending it back, is slower for a large batch, costs someone money per image, and puts your unwatermarked originals on a machine you do not control — which is a strange trade for a tool whose whole purpose is protecting your images. Doing it locally is the reason this tool has no sign-up and no usage limit. If you need the results at one size as well, run them through the bulk image resizer afterwards.

Frequently asked questions

Are my images uploaded anywhere?

No. The watermark is drawn in your browser using the canvas API. Your images and your logo never leave your computer, which is why the tool needs no account and has no usage limit.

Why is the text size a percentage instead of a point size?

Because one batch is rarely one size. A 48px caption is a billboard across a 300px thumbnail and almost invisible on a 6000px photograph, so a fixed size would be wrong for most of a mixed batch. A percentage of the image width is the same apparent size on every image, which is what lets one setting cover the whole run. It is also why the preview is exact: everything scales together.

Can I use my own logo?

Yes. Switch to an image watermark and choose a PNG, JPG or WebP file. A PNG with a transparent background is the usual choice, and its transparency is kept. The logo is never stretched — you set its width as a share of the photo and the height follows from its own proportions.

What happens if the watermark is bigger than the image?

It is centred rather than pushed off the edge. Every position is clamped so the mark stays inside the picture, and that clamp is applied to the area a rotated watermark actually sweeps out, not just to its width and height. Long text is shrunk to fit rather than running off the side.

Does watermarking a transparent PNG keep the transparency?

Yes. The output format is always the format you started with, so a PNG stays a PNG and its alpha channel comes through intact. A JPEG is given a white background before anything is drawn, because JPEG has no transparency at all.

How many images can I watermark at once?

Up to 200 per batch. They are processed a few at a time rather than all at once, so a large batch will not exhaust your browser memory. A file that turns out to be corrupt fails on its own and the rest of the batch carries on.