diff --git a/.Rbuildignore b/.Rbuildignore
index 3ec5687..012eb7c 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -1,6 +1,8 @@
-^LICENSE\.md$
+^.*~$
+^.*\.json$
 ^.*\.Rproj$
 ^\.Rproj\.user$
+^LICENSE\.md$
 ^main$
 ^pull_request$
 ^packages\.json$
diff --git a/.gitignore b/.gitignore
index 234f028..37c1341 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
+*~
+*.json
 .Rproj.user
 .Rhistory
 .RData
diff --git a/DESCRIPTION b/DESCRIPTION
index b52ce12..81b7c79 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: r.releases.utils
 Title: Utilities for An R Universe of Package Releases
 Description: Utilities for an R universe of package releases.
-Version: 0.0.7.9000
+Version: 0.0.8
 License: MIT + file LICENSE
 URL:
   https://r-releases.github.io/r.releases.utils/,
@@ -33,6 +33,7 @@ Imports:
   jsonlite,
   nanonext,
   pkgsearch,
+  utils,
   vctrs
 Encoding: UTF-8
 Language: en-US
diff --git a/NAMESPACE b/NAMESPACE
index d11de82..6aab61f 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -4,14 +4,19 @@ export(assert_cran_url)
 export(assert_package)
 export(assert_release_exists)
 export(build_universe)
+export(get_current_versions)
+export(record_versions)
 export(review_pull_request)
 export(review_pull_requests)
 export(try_message)
 importFrom(gh,gh)
 importFrom(jsonlite,parse_json)
 importFrom(jsonlite,read_json)
+importFrom(jsonlite,write_json)
 importFrom(nanonext,ncurl)
 importFrom(nanonext,parse_url)
 importFrom(nanonext,status_code)
 importFrom(pkgsearch,cran_package)
+importFrom(utils,available.packages)
+importFrom(utils,compareVersion)
 importFrom(vctrs,vec_rbind)
diff --git a/NEWS.md b/NEWS.md
index 0ff4ff0..8b9f519 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,7 +1,8 @@
-# r.releases.utils 0.0.7.9000 (development)
+# r.releases.utils 0.0.8
 
 * Use R-releases and not `r-releases` to refer to the project.
 * Edit bot messages.
+* Add `record_versions()`.
 
 # r.releases.utils 0.0.7
 
diff --git a/R/package.R b/R/package.R
index f73f627..5f884aa 100644
--- a/R/package.R
+++ b/R/package.R
@@ -3,8 +3,9 @@
 #' @name r.releases.utils-package
 #' @family help
 #' @importFrom gh gh
-#' @importFrom jsonlite parse_json read_json
+#' @importFrom jsonlite parse_json read_json write_json
 #' @importFrom nanonext ncurl parse_url status_code
 #' @importFrom pkgsearch cran_package
+#' @importFrom utils available.packages compareVersion
 #' @importFrom vctrs vec_rbind
 NULL
diff --git a/R/record_versions.R b/R/record_versions.R
new file mode 100644
index 0000000..89b660d
--- /dev/null
+++ b/R/record_versions.R
@@ -0,0 +1,100 @@
+#' @title Record the manifest of package versions.
+#' @export
+#' @description Record the manifest of versions of packages
+#'   and their hashes.
+#' @details This function tracks a manifest containing the current version,
+#'   the current hash, the highest version ever released, and
+#'   the hash of the highest version ever released. It uses this information
+#'   to determine whether the package complies with best
+#'   practices for version numbers.
+#' @return `NULL` (invisibly). Writes a package version manifest
+#'   and a manifest of version issues as JSON files.
+#' @param manifest Character of length 1, file path to the JSON manifest.
+#' @param issues Character of length 1, file path to a JSON file
+#'   which records packages with version issues.
+#' @param repos Character string of package repositories to track.
+#' @param current A data frame of current versions and hashes of packages
+#'   in `repos`. This argument is exposed for testing only.
+#' @param check_hash Logical of length 1, check hashes when judging package
+#'   version compliance. This allows [record_versions()] to flag packages
+#'   that create new releases but keep the same version number.
+record_versions <- function(
+  manifest = "versions.json",
+  issues = "version_issues.json",
+  repos = "https://r-releases.r-universe.dev",
+  current = r.releases.utils::get_current_versions(repos = repos),
+  check_hash = TRUE
+) {
+  if (!file.exists(manifest)) {
+    jsonlite::write_json(x = current, path = manifest, pretty = TRUE)
+    return(invisible())
+  }
+  previous <- read_versions_previous(manifest = manifest)
+  new <- update_version_manifest(current = current, previous = previous)
+  jsonlite::write_json(x = new, path = manifest, pretty = TRUE)
+  aligned <- versions_aligned(manifest = new, check_hash = check_hash)
+  new_issues <- new[!aligned,, drop = FALSE] # nolint
+  jsonlite::write_json(x = new_issues, path = issues, pretty = TRUE)
+  invisible()
+}
+
+#' @title Get the current versions of packages
+#' @export
+#' @keywords internal
+#' @description Get the current versions of packages in the repos.
+#' @return A data frame of packages with their current versions and hashes.
+#' @inheritParams record_versions
+get_current_versions <- function(
+  repos = "https://r-releases.r-universe.dev"
+) {
+  out <- utils::available.packages(repos = repos)
+  out <- out[, c("Package", "Version", "MD5sum")]
+  out <- as.data.frame(out)
+  colnames(out) <- c("package", "version_current", "hash_current")
+  rownames(out) <- NULL
+  out
+}
+
+read_versions_previous <- function(manifest) {
+  out <- jsonlite::read_json(path = manifest)
+  out <- do.call(what = vctrs::vec_rbind, args = out)
+  out <- lapply(out, as.character)
+  if (is.null(out$version_highest)) {
+    out$version_highest <- out$version_current
+  }
+  if (is.null(out$hash_highest)) {
+    out$hash_highest <- out$hash_current
+  }
+  out$version_current <- NULL
+  out$hash_current <- NULL
+  out
+}
+
+update_version_manifest <- function(current, previous) {
+  new <- merge(x = current, y = previous, all = TRUE)
+  incremented <- manifest_compare_versions(manifest = new) == 1L
+  new$version_highest[incremented] <- new$version_current[incremented]
+  new$hash_highest[incremented] <- new$hash_current[incremented]
+  new
+}
+
+manifest_compare_versions <- function(manifest) {
+  apply(
+    X = manifest,
+    MARGIN = 1L,
+    FUN = function(row) {
+      utils::compareVersion(
+        a = .subset2(row, "version_current"),
+        b = .subset2(row, "version_highest")
+      )
+    }
+  )
+}
+
+versions_aligned <- function(manifest, check_hash) {
+  aligned <- manifest$version_current == manifest$version_highest
+  if (check_hash) {
+    aligned <- aligned & (manifest$hash_current == manifest$hash_highest)
+  }
+  aligned
+}
diff --git a/man/get_current_versions.Rd b/man/get_current_versions.Rd
new file mode 100644
index 0000000..2f2247c
--- /dev/null
+++ b/man/get_current_versions.Rd
@@ -0,0 +1,18 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/record_versions.R
+\name{get_current_versions}
+\alias{get_current_versions}
+\title{Get the current versions of packages}
+\usage{
+get_current_versions(repos = "https://r-releases.r-universe.dev")
+}
+\arguments{
+\item{repos}{Character string of package repositories to track.}
+}
+\value{
+A data frame of packages with their current versions and hashes.
+}
+\description{
+Get the current versions of packages in the repos.
+}
+\keyword{internal}
diff --git a/man/record_versions.Rd b/man/record_versions.Rd
new file mode 100644
index 0000000..8eed436
--- /dev/null
+++ b/man/record_versions.Rd
@@ -0,0 +1,44 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/record_versions.R
+\name{record_versions}
+\alias{record_versions}
+\title{Record the manifest of package versions.}
+\usage{
+record_versions(
+  manifest = "versions.json",
+  issues = "version_issues.json",
+  repos = "https://r-releases.r-universe.dev",
+  current = r.releases.utils::get_current_versions(repos = repos),
+  check_hash = TRUE
+)
+}
+\arguments{
+\item{manifest}{Character of length 1, file path to the JSON manifest.}
+
+\item{issues}{Character of length 1, file path to a JSON file
+which records packages with version issues.}
+
+\item{repos}{Character string of package repositories to track.}
+
+\item{current}{A data frame of current versions and hashes of packages
+in \code{repos}. This argument is exposed for testing only.}
+
+\item{check_hash}{Logical of length 1, check hashes when judging package
+version compliance. This allows \code{\link[=record_versions]{record_versions()}} to flag packages
+that create new releases but keep the same version number.}
+}
+\value{
+\code{NULL} (invisibly). Writes a package version manifest
+and a manifest of version issues as JSON files.
+}
+\description{
+Record the manifest of versions of packages
+and their hashes.
+}
+\details{
+This function tracks a manifest containing the current version,
+the current hash, the highest version ever released, and
+the hash of the highest version ever released. It uses this information
+to determine whether the package complies with best
+practices for version numbers.
+}
diff --git a/tests/test-record_versions.R b/tests/test-record_versions.R
new file mode 100644
index 0000000..c845392
--- /dev/null
+++ b/tests/test-record_versions.R
@@ -0,0 +1,223 @@
+# Temporary files used in the mock test.
+manifest <- tempfile()
+issues <- tempfile()
+
+# First update to the manifest.
+contents <- data.frame(
+  package = c(
+    "package_unmodified",
+    "version_decremented",
+    "version_incremented",
+    "version_unmodified"
+  ),
+  version_current = rep("1.0.0", 4L),
+  hash_current = rep("hash_1.0.0", 4L)
+)
+r.releases.utils::record_versions(
+  manifest = manifest,
+  issues = issues,
+  current = contents
+)
+written <- jsonlite::read_json(manifest)
+expected <- list(
+  list(
+    package = "package_unmodified",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0"
+  ),
+  list(
+    package = "version_decremented",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0"
+  ),
+  list(
+    package = "version_incremented",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0"
+  ),
+  list(
+    package = "version_unmodified",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0"
+  )
+)
+stopifnot(identical(written, expected))
+stopifnot(!file.exists(issues))
+
+# Update the manifest after no changes to packages or versions.
+r.releases.utils::record_versions(
+  manifest = manifest,
+  issues = issues,
+  current = contents
+)
+written <- jsonlite::read_json(manifest)
+expected <- list(
+  list(
+    package = "package_unmodified",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  ),
+  list(
+    package = "version_decremented",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  ),
+  list(
+    package = "version_incremented",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  ),
+  list(
+    package = "version_unmodified",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  )
+)
+stopifnot(identical(written, expected))
+stopifnot(file.exists(issues))
+stopifnot(identical(jsonlite::read_json(issues), list()))
+
+# Update the packages in all the ways indicated above.
+index <- contents$package == "version_decremented"
+contents$version_current[index] <- "0.0.1"
+contents$hash_current[index] <- "hash_0.0.1"
+index <- contents$package == "version_incremented"
+contents$version_current[index] <- "2.0.0"
+contents$hash_current[index] <- "hash_2.0.0"
+index <- contents$package == "version_unmodified"
+contents$version_current[index] <- "1.0.0"
+contents$hash_current[index] <- "hash_1.0.0-modified"
+for (index in seq_len(2L)) {
+  r.releases.utils::record_versions(
+    manifest = manifest,
+    issues = issues,
+    current = contents
+  )
+  written <- jsonlite::read_json(manifest)
+  expected <- list(
+    list(
+      package = "package_unmodified",
+      version_current = "1.0.0",
+      hash_current = "hash_1.0.0",
+      version_highest = "1.0.0",
+      hash_highest = "hash_1.0.0"
+    ),
+    list(
+      package = "version_decremented",
+      version_current = "0.0.1",
+      hash_current = "hash_0.0.1",
+      version_highest = "1.0.0",
+      hash_highest = "hash_1.0.0"
+    ),
+    list(
+      package = "version_incremented",
+      version_current = "2.0.0",
+      hash_current = "hash_2.0.0",
+      version_highest = "2.0.0",
+      hash_highest = "hash_2.0.0"
+    ),
+    list(
+      package = "version_unmodified",
+      version_current = "1.0.0",
+      hash_current = "hash_1.0.0-modified",
+      version_highest = "1.0.0",
+      hash_highest = "hash_1.0.0"
+    )
+  )
+  stopifnot(identical(written, expected))
+  stopifnot(file.exists(issues))
+  written_issues <- jsonlite::read_json(issues)
+  expected_issues <- list(
+    list(
+      package = "version_decremented",
+      version_current = "0.0.1",
+      hash_current = "hash_0.0.1",
+      version_highest = "1.0.0",
+      hash_highest = "hash_1.0.0"
+    ),
+    list(
+      package = "version_unmodified",
+      version_current = "1.0.0",
+      hash_current = "hash_1.0.0-modified",
+      version_highest = "1.0.0",
+      hash_highest = "hash_1.0.0"
+    )
+  )
+  stopifnot(identical(written_issues, expected_issues))
+}
+
+# Same, but do not check the hash.
+r.releases.utils::record_versions(
+  manifest = manifest,
+  issues = issues,
+  current = contents,
+  check_hash = FALSE
+)
+written <- jsonlite::read_json(manifest)
+expected <- list(
+  list(
+    package = "package_unmodified",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  ),
+  list(
+    package = "version_decremented",
+    version_current = "0.0.1",
+    hash_current = "hash_0.0.1",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  ),
+  list(
+    package = "version_incremented",
+    version_current = "2.0.0",
+    hash_current = "hash_2.0.0",
+    version_highest = "2.0.0",
+    hash_highest = "hash_2.0.0"
+  ),
+  list(
+    package = "version_unmodified",
+    version_current = "1.0.0",
+    hash_current = "hash_1.0.0-modified",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  )
+)
+stopifnot(identical(written, expected))
+stopifnot(file.exists(issues))
+written_issues <- jsonlite::read_json(issues)
+expected_issues <- list(
+  list(
+    package = "version_decremented",
+    version_current = "0.0.1",
+    hash_current = "hash_0.0.1",
+    version_highest = "1.0.0",
+    hash_highest = "hash_1.0.0"
+  )
+)
+stopifnot(identical(written_issues, expected_issues))
+
+# Remove temporary files
+unlink(c(manifest, issues))
+
+# The manifest can be created and updated from the actual repo.
+manifest <- tempfile()
+issues <- tempfile()
+r.releases.utils::record_versions(manifest = manifest, issues = issues)
+stopifnot(file.exists(manifest))
+r.releases.utils::record_versions(manifest = manifest, issues = issues)
+contents <- jsonlite::read_json(manifest)
+stopifnot(is.character(contents[[1L]]$package))
+stopifnot(length(contents[[1L]]$package) == 1L)
+stopifnot(file.exists(manifest))
+stopifnot(file.exists(issues))
+unlink(c(manifest, issues))