diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml
index 819db811b26a684d1b9d124842e56d783ce3af83..2dd6c293503be6305a31968075010a26e0d3be55 100644
--- a/doc/src/sgml/client-auth.sgml
+++ b/doc/src/sgml/client-auth.sgml
@@ -941,7 +941,7 @@ omicron         bryanh                  guest1
    <para>
     <literal>scram-sha-256</> performs SCRAM-SHA-256 authentication, as
     described in
-    <ulink url="https://tools.ietf.org/html/rfc5802">RFC5802</ulink>. It
+    <ulink url="https://tools.ietf.org/html/rfc7677">RFC 7677</ulink>. It
     is a challenge-response scheme, that prevents password sniffing on
     untrusted connections. It is more secure than the <literal>md5</>
     method, but might not be supported by older clients.
diff --git a/doc/src/sgml/json.sgml b/doc/src/sgml/json.sgml
index 3cf78d6394cdb601c4971a0ae0bd9d95e7832a60..7dfdf9676454ef7502d0050adeba3cf20f31e7f6 100644
--- a/doc/src/sgml/json.sgml
+++ b/doc/src/sgml/json.sgml
@@ -13,7 +13,7 @@
 
  <para>
   JSON data types are for storing JSON (JavaScript Object Notation)
-  data, as specified in <ulink url="http://rfc7159.net/rfc7159">RFC
+  data, as specified in <ulink url="https://tools.ietf.org/html/rfc7159">RFC
   7159</ulink>. Such data can also be stored as <type>text</type>, but
   the JSON data types have the advantage of enforcing that each
   stored value is valid according to the JSON rules.  There are also
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index ad5e9b95b4b73aae592b79f680afcb54bdf674dc..8e0b0b8586e85ef89cf3c47c8469428df2b1a6f6 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -775,7 +775,7 @@ PGPing PQping(const char *conninfo);
     connection parameters.  There are two accepted formats for these strings:
     plain <literal>keyword = value</literal> strings
     and URIs.  URIs generally follow
-    <ulink url="http://www.ietf.org/rfc/rfc3986.txt">RFC
+    <ulink url="https://tools.ietf.org/html/rfc3986">RFC
     3986</ulink>, except that multi-host connection strings are allowed
     as further described below.
    </para>
diff --git a/doc/src/sgml/pgcrypto.sgml b/doc/src/sgml/pgcrypto.sgml
index bf514aacf3560eeca78afff632cbfc8f612e73aa..34d8621958424ebe1ed7d5ede005fb084e7aa6ad 100644
--- a/doc/src/sgml/pgcrypto.sgml
+++ b/doc/src/sgml/pgcrypto.sgml
@@ -1317,15 +1317,15 @@ gen_random_uuid() returns uuid
 
    <itemizedlist>
     <listitem>
-     <para><ulink url="http://www.ietf.org/rfc/rfc4880.txt"></ulink></para>
+     <para><ulink url="https://tools.ietf.org/html/rfc4880"></ulink></para>
      <para>OpenPGP message format.</para>
     </listitem>
     <listitem>
-     <para><ulink url="http://www.ietf.org/rfc/rfc1321.txt"></ulink></para>
+     <para><ulink url="https://tools.ietf.org/html/rfc1321"></ulink></para>
      <para>The MD5 Message-Digest Algorithm.</para>
     </listitem>
     <listitem>
-     <para><ulink url="http://www.ietf.org/rfc/rfc2104.txt"></ulink></para>
+     <para><ulink url="https://tools.ietf.org/html/rfc2104"></ulink></para>
      <para>HMAC: Keyed-Hashing for Message Authentication.</para>
     </listitem>
     <listitem>