How to use Image Watermark
Add a custom text watermark to your images to assert copyright, protect original work, and deter unauthorised use — entirely in your browser. Customise the font, size, colour, opacity, and placement of your watermark text, preview the result live, and download the watermarked image without uploading anything to a server.
- Upload your image using the file picker or drag-and-drop.
- Type your watermark text (e.g., "© 2024 Your Name" or your website URL).
- Choose the font size, text colour, and opacity (30–50% is typical for a non-intrusive watermark).
- Select the position: centre, bottom-right corner, tile across entire image, or custom coordinates.
- Preview the result and adjust settings, then click "Download" to save the watermarked PNG.
Your data never leaves your device — 100% private processing.
Watermark placement, opacity, and deterrence strategy
Watermark effectiveness depends on placement and opacity. A corner watermark at 30% opacity is discreet but easy to crop out. A centred watermark at 60% opacity covering the main subject is harder to remove but distracts from the image. A tiled watermark repeated across the entire image at 20–30% opacity is the most theft-resistant strategy — it cannot be removed by simple cropping and covering every region requires significant effort. For commercial stock images, a tiled semi-transparent watermark over the subject is the industry standard. For social media sharing, a corner or bottom-centre watermark preserves the image aesthetics while marking ownership.
| Strategy | Opacity | Deterrence | Aesthetics |
|---|---|---|---|
| Corner mark | 30–50% | Low (croppable) | High |
| Centre overlay | 50–70% | High | Low (distracting) |
| Tiled repeat | 15–30% | Highest | Medium |
| Bottom-centre text | 40–60% | Medium | High |
Invisible and visible watermarks: a technical overview
Visible watermarks are the most practical deterrent for photographers and content creators — they are immediately obvious to viewers and signal that the image is protected. Invisible (steganographic) watermarks encode ownership data in the pixel values themselves, imperceptible to the human eye, and are used by news agencies and stock libraries for forensic attribution after theft. Invisible watermarks survive JPEG recompression, resizing, and screenshot re-capture in some implementations. This tool generates visible text watermarks, which are the most actionable protection for independent creators without a specialised forensics infrastructure.
Canvas-based text rendering for watermarks
Watermarks are composited using the Canvas 2D API's globalAlpha property, which sets the transparency for all subsequent drawing operations. The text is drawn at the specified colour and size, then the alpha channel is applied. For tiled watermarks, a repeating pattern is established by measuring the text width with ctx.measureText(), then stamping the text at regular horizontal and vertical intervals across the full canvas. The final canvas is exported as a PNG with ctx.toDataURL("image/png"), preserving full colour depth and any existing transparency in the source image.
Glossary
- Watermark
- A visible or invisible mark added to an image to assert ownership, deter copying, or enable forensic attribution.
- Opacity
- The degree of transparency of a watermark, typically expressed as a percentage (0% = invisible, 100% = fully opaque).
- Tiled watermark
- A watermark repeated in a grid pattern across the entire image surface, making removal by cropping or content-aware fill impractical.
- Steganography
- The practice of hiding information within a digital file in a way that is imperceptible to human viewers, used for invisible watermarking.
- globalAlpha
- A Canvas 2D API property that controls the transparency of drawing operations, used to render semi-transparent watermark text over images.
Related reading
Frequently Asked Questions
Why use Image Watermark?
- Tiled watermark mode covers the entire image surface so the mark cannot be removed by cropping
- Opacity control balances copyright visibility against the aesthetics of the original image
- Composites the watermark locally so the original high-resolution photo stays private
- Position options — corner, centre, or tiled — suit both discreet and maximum-deterrence uses
Common use cases
- Add a "© 2024 YourName.com" text watermark to portfolio photos before posting them online
- Apply a tiled semi-transparent studio name to proof images sent to clients for approval
- Mark real estate listing photos with an agency URL before uploading to a property portal
- Overlay a "SAMPLE" or "DRAFT" label on document images for internal review circulation
- Stamp your social handle on tutorial screenshots to credit the source after resharing
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