diff --git a/src/library/base/man/memCompress.Rd b/src/library/base/man/memCompress.Rd
index d9ad1ed99b..96e9780a4e 100644
--- a/src/library/base/man/memCompress.Rd
+++ b/src/library/base/man/memCompress.Rd
@@ -1,6 +1,6 @@
 % File src/library/base/man/memCompress.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 2009-2023 R Core Team
+% Copyright 2009-2025 R Core Team
 % Distributed under GPL 2 or later
 
 \name{memCompress}
@@ -56,9 +56,9 @@ memDecompress(from,
   \eqn{2^{31}-1}{2^31 - 1} elements.  Compression is equivalent to
   \command{bzip2 -9} (the default).
 
-  \command{zstd} compression is optional and currently uses compression
-  level 3 which gives a good compression ratio vs compression speed
-  trade-off.
+  \command{zstd} compression was introduced in \R 4.5.0: it is an
+  optional part of the \R build and currently uses compression level 3
+  which gives a good compression ratio vs compression speed trade-off.
 
   Compressing with \code{type = "xz"} is equivalent to compressing a
   file with \command{xz -9e} (including adding the \sQuote{magic}
diff --git a/src/library/base/man/readRDS.Rd b/src/library/base/man/readRDS.Rd
index 320a8d30a9..04658917a4 100644
--- a/src/library/base/man/readRDS.Rd
+++ b/src/library/base/man/readRDS.Rd
@@ -1,6 +1,6 @@
 % File src/library/base/man/serialize.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 1995-2021 R Core Team
+% Copyright 1995-2025 R Core Team
 % Distributed under GPL 2 or later
 
 \name{readRDS}
@@ -20,18 +20,18 @@ infoRDS(file)
 }
 \arguments{
   \item{object}{\R object to serialize.}
-  \item{file}{a \link{connection} or the name of the file where the \R object
-    is saved to or read from.}
+  \item{file}{a \link{connection} or the path name of the file where the
+    \R object is saved to or read from.}
   \item{ascii}{a logical.  If \code{TRUE} or \code{NA}, an ASCII
     representation is written; otherwise (default), a binary one is used.
     See the comments in the help for \code{\link{save}}.}
   \item{version}{the workspace format version to use.  \code{NULL}
-    specifies the current default version (3). The only other supported
+    specifies the current default version (3).  The only other supported
     value is 2, the default from \R 1.4.0 to \R 3.5.0.}
   \item{compress}{a logical specifying whether saving to a named file is
     to use \code{"gzip"} compression, or one of \code{"gzip"},
-    \code{"bzip2"} or \code{"xz"} to indicate the type of compression to
-    be used.  Ignored if \code{file} is a connection.}
+    \code{"bzip2"}, \code{"xz"} or \code{"zstd"} to indicate the type of
+    compression to be used.  Ignored if \code{file} is a connection.}
   \item{refhook}{a hook function for handling reference objects.}
 }
 \details{
@@ -97,6 +97,9 @@ infoRDS(file)
   machines, for example to download from a website. The
   files produced by \code{\link{save}} have a header identifying the
   file type and so are better protected against erroneous use.
+
+  \code{compress = "zstd"} was first supported in \R 4.5.0, and needs OS
+  support so is even less suited as an interchange format.
 }
 
 \seealso{
diff --git a/src/library/base/man/save.Rd b/src/library/base/man/save.Rd
index ad444c920a..d6f0d0ee62 100644
--- a/src/library/base/man/save.Rd
+++ b/src/library/base/man/save.Rd
@@ -1,6 +1,6 @@
 % File src/library/base/man/save.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 1995-2020 R Core Team
+% Copyright 1995-2025 R Core Team
 % Distributed under GPL 2 or later
 
 \name{save}
@@ -50,7 +50,7 @@ save.image(file = ".RData", version = NULL, ascii = FALSE,
   \item{compress}{logical or character string specifying whether saving
     to a named file is to use compression.  \code{TRUE} corresponds to
     \command{gzip} compression, and character strings \code{"gzip"},
-    \code{"bzip2"} or \code{"xz"} specify the type of
+    \code{"bzip2"}, \code{"xz"} or \code{"zstd"} specify the type of
     compression.  Ignored when \code{file} is a connection and
     for workspace format version 1.}
   \item{compression_level}{integer: the level of compression to be
@@ -180,12 +180,16 @@ save.image(file = ".RData", version = NULL, ascii = FALSE,
   vectors, external pointers and some S4 objects).
 
   One such \sQuote{later addition} was \link{long vectors}, introduced in \R
-  3.0.0 and loadable only on 64-bit platforms.
+  3.0.0 and loadable only on 64-bit platforms (32-bit platforms are
+  dperecated but still supported).
 
   Loading files saved with \code{ASCII = NA} requires a C99-compliant C
-  function \code{sscanf}: this is a problem on Windows, first worked
+  function \code{sscanf}: this was a problem on Windows, first worked
   around in \R 3.1.2: version-2 files in that format should be readable
   in earlier versions of \R on all other platforms.
+
+  \code{compress = "zstd"} was first supported in \R 4.5.0 and needs
+  (optional) OS support so is not recommended as an interchange format.
 }
 \seealso{
   \code{\link{dput}}, \code{\link{dump}}, \code{\link{load}},
diff --git a/src/library/tools/man/writePACKAGES.Rd b/src/library/tools/man/writePACKAGES.Rd
index 418facac92..292b21e733 100644
--- a/src/library/tools/man/writePACKAGES.Rd
+++ b/src/library/tools/man/writePACKAGES.Rd
@@ -40,7 +40,7 @@ write_PACKAGES(dir = ".", fields = NULL,
     are used.
   }
   \item{type}{
-    Type of packages: currently source \file{.tar.\{gz,bz2,xz\}} archives,
+    Type of packages: currently source \file{.tar.\{gz,bz2,xz,zstd\}} archives,
     and macOS or Windows binary (\file{.tgz} or \file{.zip},
     respectively) packages are supported.  Defaults to
     \code{"win.binary"} on Windows and to \code{"source"} otherwise.
diff --git a/src/library/utils/R/packages2.R b/src/library/utils/R/packages2.R
index f0c18caced..32c2b0926c 100644
--- a/src/library/utils/R/packages2.R
+++ b/src/library/utils/R/packages2.R
@@ -194,7 +194,7 @@ install.packages <-
     get_package_name <- function(pkg) {
         ## Since the pkg argument can be the name of a file rather than
         ## a regular package name, we have to clean that up.
-        gsub("_[.](zip|tar[.]gz|tar[.]bzip2|tar[.]xz)", "",
+        gsub("_[.](zip|tar[.](gz|bzip2|bz2|xz|zstd|xst))", "",
              gsub(.standard_regexps()$valid_package_version, "",
                   basename(pkg)))
     }
@@ -399,7 +399,7 @@ install.packages <-
             df <- function(p, destfile, method, ...)
                 download.file(p, destfile, method, mode = "wb", ...)
             urls <- unique(pkgs[web])
-            
+
             if (missing(method) || method == "auto" || method == "libcurl") {
                 # bulk download using libcurl
                 destfiles <- file.path(tmpd, basename(urls))
@@ -417,7 +417,7 @@ install.packages <-
                     } else
                         pkgs[web] <- destfiles
                 } else
-                    pkgs[web] <- NA 
+                    pkgs[web] <- NA
             } else {
                 # serial download
                 for (p in urls) {