Fwiw the XSLT implementation in Blink and WebKit is extremely inefficient. For example converting the entire document into a string, to parse it to a format tha

Fwiw the XSLT implementation in Blink and WebKit is extremely inefficient. For example converting the entire document into a string, to parse it to a format that's compatible with libxslt, to then produce a string and parse it back into a node structure again. I suspect a user space library could be similarly as effective. Ex. https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/xml/xslt_processor_libxslt.cc;l=312;drc=b8271edbc28fc426d4af05f5878c00c11bc6020f https://source.chromium.org/chromium/chromium/src/+/main:thi... https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/xml/xslt_processor.cc;l=131;drc=936810fb4d0e0b979b156d5325a52e5b6c40b088 https://source.chromium.org/chromium/chromium/src/+/main:thi... https://github.com/WebKit/WebKit/blob/65b2fb1c3c4d0e85ca39026e6d25a24638340f3c/Source/WebCore/xml/XSLTProcessorLibxslt.cpp#L266 https://github.com/WebKit/WebKit/blob/65b2fb1c3c4d0e85ca3902... Mozilla has an in-house implementation at least: https://github.com/mozilla-firefox/firefox/tree/5f99d536df020fc1e909179d06a9bac1e6900ae1/dom/xslt/xslt https://github.com/mozilla-firefox/firefox/tree/5f99d536df02... It seems like the answer to the compat issue might be the MathML approach. An outside vendor would need to contribute an implementation to every browser. Possibly taking the very inefficient route since that's easy to port.