cure53 / DOMPurify

DOMPurify DOMPurify is a DOM-only, super-fast, uber-tolerant XSS sanitizer for HTML, MathML and SVG. It's also very simple to use and get started with. DOMPurify was started in February 2014 and, meanwhile, has reached version **v3.3.3**. DOMPurify runs as JavaScript and works in all modern browsers (Safari (10+), Opera (15+), Edge, Firefox and Chrome - as well as almost anything else using Blink, Gecko or WebKit). It doesn't break on MSIE or other legacy browsers. It simply does nothing. **Note that DOMPurify v2.5.9 is the latest version supporting MSIE. For important security updates compatible with MSIE, please use the 2.x branch.** Our automated tests cover 28 different browsers right now, more to come. We also cover Node.js v20.x, v22.x, 24.x and v25.x, running DOMPurify on jsdom. Older Node versions are known to work as well, but hey... no guarantees. DOMPurify is written by security people who have vast background in web attacks and XSS. Fear not. For more details please also read about our Security Goals & Threat Model. Please, read it. Like, really. What does it do? DOMPurify sanitizes HTML and prevents XSS attacks. You can feed DOMPurify with string full of dirty HTML and it will return a string (unless configured otherwise) with clean HTML. DOMPurify will strip out everything that contains dangerous HTML and thereby prevent XSS attacks and other nastiness. It's also damn bloody fast. We use the technologies the browser provides and turn them into an XSS filter. The faster your browser, the faster DOMPurify will be. How do I use it? It's easy. Just include DOMPurify on your website. Using the unminified version (source-map available) Using the minified and tested production version (source-map available) Afterwards you can sanitize strings by executing the following code: Or maybe this, if you love working with Angular or alike: The resulting HTML can be written into a DOM element using or the DOM using . That is fully up to you. Note that by default, we permit HTML, SVG **and** MathML. If you only need HTML, which might be a very common use-case, you can easily set that up as well: Is there any foot-gun potential? Well, please note, if you _first_ sanitize HTML and then modify it _afterwards_, you might easily **void the effects of sanitization**. If you feed the sanitized markup to another library _after_ sanitization, please be certain that the library doesn't mess around with the HTML on its own. Okay, makes sense, let's move on After sanitizing your markup, you can also have a look at the property and find out, what elements and attributes were thrown out. Please **do not use** this property for making any security critical decisions. This is just a little helper for curious minds. Running DOMPurify on the server DOMPurify technically also works server-side with Node.js. Our support strives to follow the Node.js release cycle. Running DOMPurify on the server requires a DOM to be present, which is probably no surprise. Usually, jsdom is the tool of choice and we **strongly recommend** to use the latest version of _jsdom_. Why? Because older versions of _jsdom_ are known to be buggy in ways that result in XSS _even if_ DOMPurify does everything 100% correctly. There are **known attack vectors** in, e.g. _jsdom v19.0.0_ that are fixed in _jsdom v20.0.0_ - and we really recommend to keep _jsdom_ up to date because of that. Please also be aware that tools like happy-dom exist but **are not considered safe** at this point. Combining DOMPurify with _happy-dom_ is currently not recommended and will likely lead to XSS. Other than that, you are fine to use DOMPurify on the server. Probably. This really depends on _jsdom_ or whatever DOM you utilize server-side. If you can live with that, this is how you get it to work: For _jsdom_ (please use an up-to-date version), this should do the trick: Or even this, if you prefer working with imports: If you have problems making it work in your specific setup, consider looking at the amazing isomorphic-dompurify project which solves lots of problems people might run into. Is there a demo? Of course there is a demo! Play with DOMPurify What if I find a _security_ bug? First of all, please immediately contact us via email so we can work on a fix. PGP key Also, you probably qualify for a bug bounty! The fine folks over at Fastmail use DOMPurify for their services and added our library to their bug bounty scope. So, if you find a way to bypass or weaken DOMPurify, please also have a look at their website and the bug bounty info. Some purification samples please? How does purified markup look like? Well, the demo shows it for a big bunch of nasty elements. But let's also show some smaller examples! What is supported? DOMPurify currently supports HTML5, SVG and MathML. DOMPurify per default allows CSS, HTML custom data attributes. DOMPurify also supports the Shadow DOM - and sanitizes DOM templates recursively. DOMPurify also allows you to sanitize HTML for being used with the jQuery and API without any known problems. What about legacy browsers like Internet Explorer? DOMPurify does nothing at all. It simply returns exactly the string that you fed it. DOMPurify exposes a property called , which tells you whether it will be able to do its job, so you can come up with your own backup plan. What about DOMPurify and Trusted Types? In version 1.0.9, support for Trusted Types API was added to DOMPurify. In version 2.0.0, a config flag was added to control DOMPurify's behavior regarding this. When is used in an environment where the Trusted Types API is available and is set to , it tries to return a value instead of a string (the behavior for and config options does not change). Note that in order to create a policy in using DOMPurify, is required, as expects a normal string, not . The example below shows this. Can I configure DOMPurify? Yes. The included default configuration values are pretty good already - b…