CanvasFingerprintBlock
Malware Detected
This extension has been flagged as potentially malicious.
Extension Delisted
This extension is no longer available in the official store. Delisted on 2025-09-15.
Protect your privacy. Prevent webpages from tracking you by your browser's HTML canvas fingerprint.
IMPORTANT: If the extension does not work on a specific site, please post the details in the SUPPORT section, as this will help me fix it. It is pointless to complain that it doesn’t work without posting the details. Thank you.
RELEASES
Version 1.5 (2016-Mar-06)
• Updated script-injection technique so that it works also on pages with strict CSP.
Version 1.4 (2016-Mar-05)
• Extension was (unnecessarily) trying to patch functions in a cross-origin frame (like Hangouts frame in GMail, Disqus frame in several sites, etc.) from within the outer window. This was breaking the sites’ functionality; now this is avoided.
Version 1.3 (2016-Feb-28)
• Blocked iframe[@sandbox] canvas reads are now shown properly inside popup
• More detailed information per blocking
Version 1.2 (2016-Feb-27)
• Now also blocks read attempts from canvas inside a sandboxed iframe element
DETAILS
Canvas Fingerprinting is one of latest technologies being adopted by websites to track visitors without using cookies. Such websites do this by painting an image on a hidden HTML <canvas> element and then taking a snapshot of it and posting the snapshot back to themselves. Because the exact pixel values in the drawn canvas can differ subtly from one set of hardware to another, these websites can use those differences to distinguish between visitors as well as to recognize specific visitors from one visit to the next. Which is what tracking cookies are normally used for, except that cookies may be disabled or deleted or avoided by browsing in Incognito mode, whereas to avoid Canvas Fingerprinting you need to use a tool like CanvasFingerprintBlock.
The HTML <canvas> element exposes two types of JavaScript functions: functions to draw to the canvas, and functions to export data from the canvas (for the nerds, these are toDataURL() and getImageData()). The canvas-drawing functions are not affected by CanvasFingerprintBlock, so websites that use the canvas for basic drawing will not be affected. On the other hand, when a website tries to export data from the canvas, CanvasFingerprintBlock will “fool” the website by showing it a blank canvas instead of the canvas containing the actual pixels. If the website is reading the canvas data to generate a fingerprint, the generated fingerprint will be useless because CanvasFingerprintBlock makes everyone’s fingerprint look the same.
If a little red fingerprint icon appears in the address bar beside the Bookmark ☆ icon, it means that the website you are visiting has tried to access the data of at least one canvas, and CanvasFingerprintBlock has blocked it. You will be surprised to discover how many websites employ Canvas Fingerprinting! Most websites are quite sneaky in how they create the fingerprint; the canvas is always hidden, and usually the canvas would have already been created, read and removed by the time the website has finished loading! Of course you will be curious to inspect what was being drawn right under your nose, and CanvasFingerprintBlock will let you see it by clicking on the little red fingerprint icon.
Lastly, it is noteworthy to mention that not all websites that are trying to export data from a canvas are doing it maliciously. For example, some photo uploaders will let you edit your photo on a canvas and when you are ready will export the edited photo and upload it to the server. Or some other websites will use a “rough” canvas to draw a gradient or pattern, and will then export the canvas to use that pattern somewhere else on the page. When you see the little red fingerprint icon, by clicking on it it is usually easy to tell whether the blocked canvas was drawn for fingerprinting purposes or not. However it is not so simple to detect this automatically. So for the time being, CanvasFingerprintBlock will block all canvas data exports, and the only way of allowing a canvas read is to disable the extension temporarily. This will be fixed in a future update of CanvasFingerprintBlock.
You may test CanvasFingerprintBlock on this website: http://www.browserleaks.com/canvas
Note: If you are a user of Chrome’s Incognito mode, then to be fully protected it is advisable to enable the CanvasFingerprintBlock extension also in Incognito mode (check “Allow in Incognito”).
Latest reviews
It blocks Excel for Office365 workbooks from running in Chrome and there is no toggle to disable for specific sites, so guess I'll just delete the extension
Doesn't work on https://fingerprintjs.com/demo
This extension will cause canvas.toDataURL to not work properly and return transparent png !!!
works great
Works great. The only thing it could use is a randomize feature. Randomization would break a lot of tracking, where as blocking just means they have a little bit less data to identify you with.
CanvasFingerprintBlock consistently breaks the browserleaks.com/canvas site and crashes my 66.0.3359.81 beta Chrome browser at the same time.
i can't remove it from my chrome
It causes Google homepage not to work when clicking on their animated logos. (No white list). I have no clue if this thing works and have to way to test it.
Google Chrome 63 не меняет Canvas. Плохо.
Make NO DIFFERENCE at https://panopticlick.eff.org/results?&t=111&dnt=111#fingerprintTable
Fingerprint does not change and provides 7 bits of identifying info Bad. Uninstall.
It is not possible to disable on specific sites that shows images I want to see. Missing the white-list option!
Just received this result after installing: Your browser fingerprint appears to be unique among the 308,797 tested so far. Currently, we estimate that your browser has a fingerprint that conveys at least 18.24 bits of identifying information.
Not work
works ok but gives the SAME fingerprint to all users with this extension, on top of that some site now will have a blank page while using this canvasfingerprint block. it would be better if it faked a new fingerprint every page refresh. i guess being in a swarm with the same fingerprint does minimize your individual detection
Geht nicht mehr
Geht nicht. Finger weg davon!
Works well, seems to block canvas fingerprint attempts. Now all wee need is a few 10's of thousands more users so we are more unique. Right now this blocking tool can also be used as a unique identifier.
does not work on this page: https://panopticlick.eff.org/results?&a=111&t=111&dnt=111
This is an awesome extension and works very well but it *really* needs to be able to white-list by domain, preferably with an option to do so for the current session only.
Doesn`t work. panopticlick.eff.org shows my canvas fingerprint ID.
Funktioniert nicht
Can't whitelist certain sites.
Updated, newer version works well. Thanks ***** doesnt work in chrome http://www.browserleaks.com/canvas
Excellent extension. It does work fine on this website too http://www.browserleaks.com/canvas
False positives, doesn't work on true positives.
It doesn't seem to work on the browserleaks page.
Doesn't seem to work again http://www.browserleaks.com/canvas
