Change documentation to point at Matrix rather than IRC. (#29484)

diff --git a/CODE_OF_CONDUCT.md b/CODE_OF_CONDUCT.md
index 8cae1f5..dae98ee 100644
--- a/CODE_OF_CONDUCT.md
+++ b/CODE_OF_CONDUCT.md
@@ -57,11 +57,12 @@
 
 ## Scope
 
-This Code of Conduct applies within all community spaces, and also applies when
-an individual is officially representing the community in public spaces.
-Examples of representing our community include official IRC channels (#testing
-on irc.w3.org); GitHub repositories under the web-platform-tests organization;
-and the public-test-infra@w3.org mailing list.
+This Code of Conduct applies within all community spaces, and also
+applies when an individual is officially representing the community in
+public spaces.  Examples of representing our community include
+the official Matrix channel (wpt:matrix.org); GitHub repositories under
+the web-platform-tests organization; and the public-test-infra@w3.org
+mailing list.
 
 There may arise situations where both the WPT code of conduct and that of
 another organization (such as the WHATWG or W3C) may apply.
diff --git a/README.md b/README.md
index 5946646..5de4d23 100644
--- a/README.md
+++ b/README.md
@@ -26,11 +26,9 @@
   Internet-enabled browser of their choice
 - [wpt.fyi](https://wpt.fyi): an archive of test results collected from an
   array of web browsers on a regular basis
-- [Real-time chat room](http://irc.w3.org/?channels=testing): the
-  [IRC](http://www.irchelp.org/) chat room named `#testing` on
-  [irc.w3.org](https://www.w3.org/wiki/IRC); includes participants located
-  around the world, but busiest during the European working day; [all
-  discussion is archived here](https://w3.logbot.info/testing)
+- [Real-time chat room](https://app.element.io/#/room/#wpt:matrix.org): the
+  `wpt:matrix.org` matrix channel; includes participants located
+  around the world, but busiest during the European working day.
 - [Mailing list](https://lists.w3.org/Archives/Public/public-test-infra/): a
   public and low-traffic discussion list
 - [RFCs](https://github.com/web-platform-tests/rfcs): a repo for requesting
diff --git a/docs/index.md b/docs/index.md
index b0ba034..799c8e4 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -24,11 +24,9 @@
   Internet-enabled browser of their choice
 - [wpt.fyi](https://wpt.fyi): an archive of test results collected from an
   array of web browsers on a regular basis
-- [Real-time chat room](http://irc.w3.org/?channels=testing): the
-  [IRC](http://www.irchelp.org/) chat room named `#testing` on
-  [irc.w3.org](https://www.w3.org/wiki/IRC); includes participants located
-  around the world, but busiest during the European working day; [all
-  discussion is archived here](https://w3.logbot.info/testing)
+- [Real-time chat room](https://app.element.io/#/room/#wpt:matrix.org): the
+  `wpt:matrix.org` matrix channel; includes participants located
+  around the world, but busiest during the European working day.
 - [Mailing list](https://lists.w3.org/Archives/Public/public-test-infra/): a
   public and low-traffic discussion list
 
diff --git a/docs/running-tests/custom-runner.md b/docs/running-tests/custom-runner.md
index 4e860ed..029a877 100644
--- a/docs/running-tests/custom-runner.md
+++ b/docs/running-tests/custom-runner.md
@@ -11,12 +11,11 @@
 considered the canonical definition of how to enumerate tests and find
 their type in the repository.
 
-For test execution, please read the documentation for the various test types
-very carefully and then check your understanding on
-the [mailing list][public-test-infra] or [IRC][] ([webclient][web irc], join
-channel `#testing`). It's possible edge-case behavior isn't properly
-documented!
+For test execution, please read the documentation for the various test
+types very carefully and then check your understanding on the [mailing
+list][public-test-infra] or [matrix][matrix]. It's possible edge-case
+behavior isn't properly documented!
 
 [public-test-infra]: https://lists.w3.org/Archives/Public/public-test-infra/
-[IRC]: irc://irc.w3.org:6667/testing
+[matrix]: https://app.element.io/#/room/#wpt:matrix.org
 [web irc]: http://irc.w3.org
diff --git a/docs/writing-tests/general-guidelines.md b/docs/writing-tests/general-guidelines.md
index 1ec9117..a4278a7 100644
--- a/docs/writing-tests/general-guidelines.md
+++ b/docs/writing-tests/general-guidelines.md
@@ -74,9 +74,9 @@
   features])
 - [WebDriver specification tests](wdspec) are expressed as Python files
 
-The best way to determine how to format a new test is to look at how similar
-tests have been formatted. You can also ask for advice in [the project's IRC
-room][IRC].
+The best way to determine how to format a new test is to look at how
+similar tests have been formatted. You can also ask for advice in [the
+project's matrix channel][matrix].
 
 
 ### Character Encoding
@@ -216,7 +216,7 @@
 [server features]: server-features
 [assumptions]: assumptions
 [ahem]: ahem
-[IRC]: irc://irc.w3.org:6667/testing
+[matrix]: https://app.element.io/#/room/#wpt:matrix.org
 [lint-tool]: lint-tool
 [css-metadata]: css-metadata
 [css-user-styles]: css-user-styles
diff --git a/docs/writing-tests/submission-process.md b/docs/writing-tests/submission-process.md
index c6268f9..b3ae83b 100644
--- a/docs/writing-tests/submission-process.md
+++ b/docs/writing-tests/submission-process.md
@@ -30,10 +30,10 @@
 have to go through all the tests and ensure that they match the specification
 correctly. But we look at all of them, and take everything that we can.
 
-Hop on to the [mailing list][public-test-infra] or [IRC][]
-([webclient][web irc], join channel `#testing`) if you have an issue.  There is
-no need to announce your review request, as soon as you make a Pull Request
-GitHub will inform interested parties.
+Hop on to the [mailing list][public-test-infra] or [matrix
+channel][matrix] if you have an issue.  There is no need to announce
+your review request; as soon as you make a Pull Request, GitHub will
+inform interested parties.
 
 ## Previews
 
@@ -60,5 +60,4 @@
 [repo]: https://github.com/web-platform-tests/wpt/
 [github flow]: https://guides.github.com/introduction/flow/
 [public-test-infra]: https://lists.w3.org/Archives/Public/public-test-infra/
-[IRC]: irc://irc.w3.org:6667/testing
-[web irc]: http://irc.w3.org
+[matrix]: https://app.element.io/#/room/#wpt:matrix.org