Firefox Browser Add-ons
  • Extensions
  • Themes
    • for Firefox
    • Dictionaries & Language Packs
    • Other Browser Sites
    • Add-ons for Android
Log in
Preview of StampThat

StampThat by Nicolas Micaux

Protect yourself from Identity Theft by using Stamp That!

0 (0 reviews)0 (0 reviews)
Download Firefox and get the extension
Download file

Extension Metadata

Screenshots
install StampThat now for freeStampThat popup asks you whether you want to watermark sent file or notStampThat watermarks make reusing the document impossible for scammersStampThat offers a lot of settings: rules to auto-watermark some file types, or files on some domains, ...
About this extension
StampThat automatically watermarks your documents the moment you upload them—anywhere on the web: email, Google Drive, WhatsApp Web, administration portals, bank forms, and more.

A watermarked ID or contract cannot be reused to take out loans or commit fraud. With StampThat, your documents stay usable for their purpose, but worthless to hackers.

How it works
- 📤 Detects document uploads automatically (drag & drop, paste, file inputs)
- ✍️ Adds customizable watermark instantly
- 🌐 Works on any website
- ✅ Supports images, PDFs, and ZIP archives
- 🔍 Format whitelists & blacklists for full control

All processing happens locally in your browser. Your files never leave your computer.

Built for people who share sensitive documents
- Anyone looking for a rent, submitting documents to banks, landlords, or administrations
- Freelancers sending IDs or contracts
- Students applying to job offers

Privacy by design
- ✅ 100% local processing
- 🚫 No data collection

Stamp That is available in 18 languages.
  • 🆓 FREE weekly quota included
  • 💳 Buy credits for unlimited usage

👉 Install the Stamp That Chrome extension in one click and protect your personal data BEFORE sharing, NOT WHEN IT'S TOO LATE.
Rated 0 by 0 reviewers
Sign in to rate this extension
There are no ratings yet

Star rating saved

5
0
4
0
3
0
2
0
1
0
No reviews yet
Permissions and data

Required permissions:

  • Access your data for all websites

Data collection:

  • The developer says this extension doesn't require data collection.

Optional data collection, according to the developer:

  • Technical and interaction data
Learn more
More information
Add-on Links
  • Support Email
Version
1.0.5
Size
2.33 MB
Last updated
6 days ago (Jan 13, 2026)
Related Categories
  • Privacy & Security
License
All Rights Reserved
Version History
  • See all versions
Tags
  • privacy
  • security
Add to collection
Report this add-on
Go to Mozilla’s homepage

Add-ons

  • About
  • Firefox Add-ons Blog
  • Extension Workshop
  • Developer Hub
  • Developer Policies
  • Community Blog
  • Forum
  • Report a bug
  • Review Guide

Browsers

  • Desktop
  • Mobile
  • Enterprise

Products

  • Browsers
  • VPN
  • Relay
  • Monitor
  • Pocket
  • Bluesky (@firefox.com)
  • Instagram (Firefox)
  • YouTube (firefoxchannel)
  • Privacy
  • Cookies
  • Legal

Except where otherwise noted, content on this site is licensed under the Creative Commons Attribution Share-Alike License v3.0 or any later version.