🖼️ Image Watermark Tool
By ToolNimba Editorial Team · Updated 2026-06-19
PNG, JPEG, WebP and GIF are supported. Your image never leaves your browser.
Upload an image to begin. Everything runs locally on your device.
This image watermark tool lets you stamp a text watermark onto any photo right in your browser. Upload an image, type your watermark text, then fine-tune the position, opacity, font size and color until it looks right. The preview updates instantly and you can download the finished image with one click. Nothing is uploaded to a server, so your photos stay private on your own device.
What is the Image Watermark Tool?
A watermark is a piece of text or a logo placed over an image to mark ownership, discourage unauthorized reuse, or simply brand your work. The most common kind is a semi-transparent text watermark, for example a name, website or copyright line, sitting in a corner of the photo. Because it is partly see-through, it identifies the source without hiding the picture underneath.
This tool builds the watermark entirely with the HTML canvas. When you load an image it is drawn onto a canvas at its full native resolution, then your text is painted on top using the font size, color and opacity you choose. Opacity is the key setting: a value around 40% to 60% is usually visible enough to claim the image yet light enough not to spoil it. A subtle drop shadow is added by default so light text stays readable on light backgrounds and dark text on dark ones.
Everything happens locally in your browser using FileReader and the canvas API, with no network requests. When you download, the canvas is exported with toBlob as a PNG, which preserves the watermark crisply and supports transparency. Because the watermark is rendered at full resolution, it scales with the image rather than looking pixelated, and the original file on your computer is never modified or sent anywhere.
When to use it
- Adding a copyright line or your name to photos before posting them on social media or a portfolio.
- Branding product images, screenshots or infographics with a website URL so reshares still point back to you.
- Marking draft or sample images with text like "PROOF" or "SAMPLE" before a client approves the final version.
- Protecting images you sell or license by stamping ownership text that discourages casual copying.
How to use the Image Watermark Tool
- Choose an image file from your device. It loads instantly and stays in your browser.
- Type the watermark text you want, such as your name, a copyright symbol, or a website.
- Pick a position (a corner or the center) and adjust the color, font size and opacity.
- Toggle the shadow on or off for legibility, then check the live preview.
- Click Download watermarked image to save the result as a PNG.
Formula & method
Worked examples
A 1600 px wide photo, watermark font size set to 6%.
- font size = (6 ÷ 100) × 1600 = 96 px
- Opacity slider at 50% gives an alpha of 0.5
- White text #ffffff becomes fill rgba(255, 255, 255, 0.5)
- With position bottom-right, the text is anchored to the lower-right corner inside the margin
Result: A semi-transparent 96 px white watermark sits in the bottom-right corner.
An 800 px wide image, font size 10%, opacity 80%, center position.
- font size = (10 ÷ 100) × 800 = 80 px
- Opacity 80% gives an alpha of 0.8
- Center position anchors the text at (400, the vertical middle) with centered alignment
Result: A bold 80 px watermark sits centered across the middle of the image at 80% opacity.
Suggested watermark settings by goal
| Goal | Position | Opacity | Font size |
|---|---|---|---|
| Subtle branding | Bottom right | 30% to 45% | 4% to 6% |
| Clear ownership | Bottom right or left | 50% to 65% | 6% to 8% |
| Strong anti-theft | Center | 40% to 60% | 10% to 16% |
| Draft or proof label | Center | 50% to 70% | 12% to 20% |
Common mistakes to avoid
- Setting opacity too high. A watermark at 90% or 100% opacity covers the image and looks unprofessional. Most watermarks sit between 30% and 60% so they are visible without overwhelming the photo.
- Using a color that blends into the background. White text vanishes on a bright sky and black text disappears on a dark scene. Keep the shadow on, or switch the text color to contrast with the area where the watermark sits.
- Placing the watermark where it is easy to crop out. A tiny corner watermark can be cropped away in seconds. For stronger protection use the center position or a larger size so removing it would damage the image.
- Expecting a watermark to be uncopyable. A visible text watermark deters casual reuse but a determined editor can sometimes remove it. Treat it as a deterrent and a credit, not a guarantee against theft.
Glossary
- Watermark
- Text or a logo overlaid on an image to mark ownership or source, usually semi-transparent so the picture stays visible.
- Opacity
- How solid the watermark text appears, from 0% (invisible) to 100% (fully opaque). Lower values let the image show through.
- Canvas
- The HTML drawing surface this tool uses to combine your image and the watermark text entirely in the browser.
- PNG
- A lossless image format that preserves sharp text and transparency, used here for the downloaded watermarked file.
- Anchor
- The reference point the text is aligned to, such as the bottom-right corner or the center of the image.
Frequently asked questions
How do I add a watermark to a photo?
Upload your image, type the text you want as a watermark, then choose a position, color, font size and opacity. The preview updates as you go, and the Download button saves the watermarked image to your device.
Is this image watermark tool free?
Yes. The tool is completely free with no sign-up, no limits and no watermark of our own added to your image. You only see the text you type.
Are my images uploaded to a server?
No. Everything runs in your browser using the canvas and FileReader APIs. Your photo is never sent over the network, so it stays private on your own device.
What image formats can I watermark?
You can load PNG, JPEG, WebP and GIF images. The watermarked result is exported as a PNG, which keeps the text sharp and supports transparency.
What opacity should I use for a watermark?
For most photos an opacity between 40% and 60% works well: visible enough to claim the image but light enough not to spoil it. Lower it toward 30% for subtle branding or raise it for a stronger mark.
Can I add an image or logo as the watermark instead of text?
This tool overlays text watermarks, including a copyright symbol or website. For a logo watermark you would composite a second image, which this tool does not currently do, so it focuses on clean, adjustable text.