diff --git a/libpng.3 b/libpng.3
index ce0159b0a..3079c7dca 100644
--- a/libpng.3
+++ b/libpng.3
@@ -5987,7 +5987,7 @@ release number plus "betaNN" or "rcNN".
 .LP
 .IR libpng :
 .IP
-http://libpng.sourceforge.net (follow the [DOWNLOAD] link)
+https://libpng.sourceforge.io/ (follow the [DOWNLOAD] link)
 http://www.libpng.org/pub/png
 
 .LP
@@ -5997,7 +5997,7 @@ http://www.libpng.org/pub/png
 .I libpng
 or at
 .br
-ftp://ftp.info-zip.org/pub/infozip/zlib
+http://zlib.net/
 
 .LP
 .IR PNG specification: RFC 2083
@@ -6006,11 +6006,11 @@ ftp://ftp.info-zip.org/pub/infozip/zlib
 .I libpng
 or at
 .br
-ftp://ftp.rfc-editor.org:/in-notes/rfc2083.txt
+https://www.ietf.org/rfc/rfc2083.txt
 .br
 or (as a W3C Recommendation) at
 .br
-http://www.w3.org/TR/REC-png.html
+https://www.w3.org/TR/REC-png.html
 
 .LP
 In the case of any inconsistency between the PNG specification