Embed blind watermarks locally JPG · PNG · WebP
Pure browser tool · No backend · Works offline once loaded · BlindWMLocal
JPG, PNG, WebP in · up to 10 MB · disconnect before choosing a file to verify offline mode
Fixed slot for extraction — shorter text is padded with spaces. Site default 32; clear to match text length only.
Preview & download
Download format
Important — keep extract parameters
Blind watermark guides
Practical notes on embedding, extracting, and testing invisible watermarks — pure browser, no backend, offline once loaded.
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Embed blind watermarks without uploading your image
Why browser-only beats cloud APIs — including offline verification before you choose a file.
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What
_wm_lenand_lvlmean in download filenamesHow BlindWMLocal encodes extract parameters so you do not have to guess later.
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JPEG export quality vs watermark survival
When heavy compression breaks extraction — and how to test on the Extract page.
Free blind watermark tool — pure browser, no backend
BlindWMLocal (part of ShrinkLocal) lets you embed a hidden text string into photos for traceability and leak investigation. Unlike cloud watermark services, there is no backend image API: the blind-watermark library runs in JavaScript inside your browser, and your files never leave the device.
Once the page and scripts have loaded, you can disconnect the network before choosing a file and still embed, extract, or screen — a simple way to confirm nothing is uploaded.
Download filenames include _wm_len{N}_lvl{L} so you can extract later without guessing parameters. Need smaller files? Use ShrinkLocal compress after embedding — also browser-only, no upload.
Read how it works for offline and DevTools checks, or browse the BlindWMLocal blog for guides on local embed, filename hints, and JPEG quality vs extraction.
Frequently asked questions
Does BlindWMLocal upload my images?
No. There is no backend that processes photos. Embed, extract, and detect run in your browser — only static
.jsfiles load from this site.Can I use it offline?
Yes, after the page and library finish loading. Disconnect Wi‑Fi or enable airplane mode before you choose an image — the tool still works. That proves your files are not sent to a server.
Do I need to register or log in?
No account, no paywall. Same local-first approach as ShrinkLocal compression.
Why can I download JPEG after choosing a JPG?
The library embeds into a PNG buffer first; your browser converts to JPEG, PNG, or WebP locally — no server involved.
Will compression remove the watermark?
Heavy compression can weaken it. Use JPEG quality ≥ 85% and test on the Extract page.
How is this different from cloud watermark APIs?
Cloud APIs receive your image bytes on their servers. BlindWMLocal has no image upload endpoint — useful for GDPR and confidential assets.