diff --git a/src/identifiers.md b/src/identifiers.md
index 5abe303ca2..bb71f3ff64 100644
--- a/src/identifiers.md
+++ b/src/identifiers.md
@@ -85,5 +85,5 @@ It is an error to use the [RESERVED_RAW_IDENTIFIER] token.
 [proc-macro]: procedural-macros.md
 [reserved]: keywords.md#reserved-keywords
 [strict]: keywords.md#strict-keywords
-[UAX15]: https://www.unicode.org/reports/tr15/tr15-57.html
-[UAX31]: https://www.unicode.org/reports/tr31/tr31-43.html
+[UAX15]: https://www.unicode.org/reports/tr15
+[UAX31]: https://www.unicode.org/reports/tr31
diff --git a/src/input-format.md b/src/input-format.md
index 88ab3658ba..ad6b93ba6b 100644
--- a/src/input-format.md
+++ b/src/input-format.md
@@ -21,11 +21,14 @@ r[input.encoding]
 ## Source encoding
 
 r[input.encoding.utf8]
-Each source file is interpreted as a sequence of Unicode characters encoded in UTF-8.
+Each source file is interpreted as a sequence of Unicode characters encoded in UTF-8. Information on this encoding can be found at <https://www.unicode.org/versions/latest/core-spec/chapter-3/#G31703>.
 
 r[input.encoding.invalid]
 It is an error if the file is not valid UTF-8.
 
+r[input.encoding.unicode-version]
+Unicode is an evolving standard, which Rust tracks. The exact version used by the Rust language is delegated to the standard library, documented at [`char::UNICODE_VERSION`].
+
 r[input.byte-order-mark]
 ## Byte order mark removal
 
@@ -62,3 +65,4 @@ The resulting sequence of characters is then converted into tokens as described
 [Crates and source files]: crates-and-source-files.md
 [shebang]: shebang.md
 [whitespace]: whitespace.md
+[`char::UNICODE_VERSION`]: https://doc.rust-lang.org/nightly/std/primitive.char.html#associatedconstant.UNICODE_VERSION