Why I built XMLNest

Why is XSLT not working in Chrome?

If an XML page that used to look like a tidy table now shows a warning and raw tags, the cause is in the browser, not on the site. Chrome has announced that it is removing its built-in support for XSLT. XSLT is the language that turns an XML file into a readable page, using an XSL stylesheet that the file points to.

Chrome’s announcement gives the date. From Chrome 158, on 17 November 2026, XSLT stops working on Stable releases for everyone, except sites in Chrome’s origin trial and browsers managed with an enterprise policy.

The reason Chrome gives is security. The libraries that run these transformations are complex C and C++ code, and that kind of code is prone to memory safety bugs. I understand the decision. But a change like this always lands somewhere: on real pages, and on the people who open them.

When the stylesheet is no longer applied, the table, the headings and the links it built disappear. Chrome shows a warning banner that links to a Chrome Web Store search for an extension, and the page itself shows the raw XML: tags and text, with no layout. For the full timeline and the options for site owners, read what to do now that XSLT is removed from Chrome.

Which XML pages break on 17 November?

Chrome says XSLT is rare on the web. Yet it sits behind pages that many people open without knowing it:

• WordPress sitemaps. Since WordPress 5.5, a WordPress site publishes a sitemap index at /wp-sitemap.xml, and WordPress provides XSL stylesheets to style all its sitemaps. Here is how to view a WordPress sitemap, before and after the change.
• SEO plugin sitemaps. Yoast SEO’s sitemap index and sitemaps reference an XSL file that gives them their layout.
• Styled RSS feeds. Chrome notes that many RSS and Atom feeds use XSLT so that people can read them when they open the feed directly in the browser. If a feed already looks like code to you, see why an RSS feed shows as plain text in Chrome.
• Device status pages. Chrome also mentions devices that generate XML for their users on the local network, and adds that many of them are difficult or impossible to update.

Why a designer cares about raw XML

I have been designing web products for 12 years. A large part of that work is making information clear for people who are not developers.

Raw XML is the opposite of that. It is written for programs, not for people. Someone checking their sitemap, a site owner looking at a feed, or a listener who clicks a podcast link should not have to read angle brackets to find what they came for. The same goes for anyone who simply wants to open an XML file in Chrome and understand what is inside.

That is the gap I wanted to close. Not with a developer tool, but with something a person can install and forget, until the day they need it.

What XMLNest does: an XML viewer and XSLT polyfill for Chrome

XMLNest is a free Chrome extension. Here is what it does:

• It shows XML pages that use an XSL stylesheet (XSLT 1.0) the way Chrome used to show them. The stylesheet runs in an isolated sandbox.
• It displays any XML document as a tree you can fold and search, and as formatted source.
• It opens RSS and Atom feeds in a reader view, with a built-in podcast player.
• It turns XML sitemaps into a table you can filter, sort and export to CSV or JSON.
• It opens XML files from your computer, once you allow local files.
• It has light and dark themes, and it is available in 55 languages.

Two principles shaped it. Privacy first: it collects no data, shows no ads and needs no account. Nothing you open is collected or sent anywhere, and the few settings it saves stay in your browser. Permissions only when they are needed: it is installed with no access to any site. You turn it on everywhere in one click, or site by site, when you decide you need it. Scripts inside a transformed page stay off unless you allow them for that site.

XMLNest or the official XSLT Polyfill extension?

Chrome’s announcement links to one extension, the official one, and many people have found it. According to Chrome Web Store data for its listing, it went from about 6,000 to about 70,000 users between 28 September and 4 October 2026.

Both extensions use the same open-source engine, xslt-polyfill. The differences are simple:

• The official extension also adds XSLT to the JavaScript of ordinary HTML pages, through XSLTProcessor. XMLNest does not. If a site or a tool you use depends on that, choose the official extension.
• XMLNest adds reader, tree and source views for XML documents, and asks for no site access at install.
• XMLNest does not apply XSL stylesheets to files on your computer, just as Chrome never did.

I would rather say this clearly than have someone install the wrong tool. You can read how XMLNest works and which permissions it asks for in more detail.

What comes next

XMLNest is coming soon to the Chrome Web Store, before 17 November.

Until then, the guides linked above explain what changes and what your options are, as a visitor or as a site owner. If you have a question, or an XML page that does not display the way you expect, write to me at contact@xmlnest.com.