Image Watermark Embedder
Add visible copyright overlay and/or invisible DWT+DCT frequency watermark to images. Robustness survival test included. No upload — 100% client-side.
Drop your image here or click to browse
PNG, JPEG, BMP, WebP · Max 50 MB
All processing runs locally — your image never leaves your device
100% Client-Side Processing
Your image is decoded using the Canvas API in this browser tab. Nothing is uploaded. Output is always lossless PNG — watermarks are preserved exactly.
How to Add a Watermark to Your Photo (4 steps)
- Upload your photo (PNG, JPEG, BMP, or WebP). A live preview shows the visible watermark updating as you type your copyright text.
- Enter your copyright notice (e.g. '© Your Name 2026'). Toggle visible watermark (overlay) and/or invisible watermark (frequency-domain). Both can be combined for maximum protection.
- Optional: choose watermark position, opacity, font size, and invisible watermark strength (Balanced survives JPEG and social media; Archival is legal-grade).
- Click 'Protect My Image' — processing runs in your browser. Download the watermarked PNG. Use 'Open Watermark Detector' to verify protection is present.
Watermark Types & Methods
| Type | Technique | Removability | Best For |
|---|---|---|---|
| Visible — Text | Copyright text overlay at user-specified position with opacity, font, shadow, and optional tiled mode | ✅ Removable by cropping | Brand attribution, deter casual theft, stock preview mode |
| Visible — Tile | Repeating watermark grid across the full image for stock photo preview protection | ⚠️ Harder to crop fully | Stock photography, preventing unauthorized preview use |
| Invisible — Light (PSNR ~48 dB) | DWT+DCT frequency domain — extremely subtle quality impact, fragile under heavy compression | ❌ May not survive aggressive JPEG | Maximum quality images, light copyright notice |
| Invisible — Balanced (PSNR ~44 dB) | DWT+DCT — survives JPEG Q80+, social media uploads, brightness/contrast adjustments | ✅ Default recommendation | Portfolio images, social media sharing |
| Invisible — Archival (PSNR ~40 dB) | DWT+DCT — strongest survival, robust against most common processing | ✅ Legal-grade evidence | Embargoed press images, per-recipient fingerprinting |
Frequently Asked Questions
What is the difference between visible and invisible watermarks?
A visible watermark (text/logo overlay) acts as a deterrent — casual viewers see it immediately. An invisible watermark is embedded in the frequency data of the image using DWT+DCT algorithms — completely undetectable to the human eye, but verifiable with a detector. Using both provides maximum protection: the visible mark deters theft, and the invisible mark survives even if the visible one is cropped away.
Does the invisible watermark change image quality?
Yes, very slightly. At Balanced strength, PSNR is approximately 44 dB — a quality metric where 40+ dB is generally considered imperceptible. For comparison, JPEG compression typically produces 30–40 dB. The invisible watermark introduces less visible degradation than a standard JPEG save.
Will the invisible watermark survive Instagram or Twitter?
At Balanced or Archival strength, the invisible watermark survives JPEG compression at typical social media quality levels. However, extreme compression or format conversion may reduce accuracy. The robustness test (enable in Advanced) shows exact survival rates before you download.
How does the robustness test work?
After embedding, the tool simulates JPEG compression at different quality levels and brightness adjustment, then attempts to re-extract the watermark from each simulated result. Bit accuracy >75% means the watermark is readable — considered 'survived'.
What is the DWT+DCT algorithm?
Discrete Wavelet Transform + Discrete Cosine Transform. The image is first decomposed into frequency subbands using Haar wavelets. The LL (low-frequency) subband is divided into 8×8 blocks, and each block undergoes DCT. A watermark bit is embedded into the dominant DCT coefficient using quantization-index modulation (QIM). This frequency-domain approach is why the watermark survives JPEG — JPEG also operates in DCT frequency space.
Is my image uploaded to any server?
Never. All processing — visible overlay, DWT+DCT embedding, robustness testing — runs in a WebWorker inside your browser. The image never leaves your device. You can disconnect from the internet after the page loads and it still works.