diff --git a/.github/workflows/R-CMD-check.yaml b/.github/workflows/R-CMD-check.yaml
index 82195e0e..66d89692 100644
--- a/.github/workflows/R-CMD-check.yaml
+++ b/.github/workflows/R-CMD-check.yaml
@@ -1,16 +1,14 @@
-# NOTE: This workflow is overkill for most R packages
-# check-standard.yaml is likely a better choice
-# usethis::use_github_action("check-standard") will install it.
+# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
+# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
 #
-# For help debugging build failures open an issue on the RStudio community with the 'github-actions' tag.
-# https://community.rstudio.com/new-topic?category=Package%20development&tags=github-actions
+# NOTE: This workflow is overkill for most R packages and
+# check-standard.yaml is likely a better choice.
+# usethis::use_github_action("check-standard") will install it.
 on:
   push:
-    branches:
-      - master
+    branches: [main, master]
   pull_request:
-    branches:
-      - master
+    branches: [main, master]
 
 name: R-CMD-check
 
@@ -26,79 +24,33 @@ jobs:
         config:
           - {os: macOS-latest,   r: 'release'}
           - {os: windows-latest, r: 'release'}
-          - {os: windows-latest, r: '3.6'}
-          - {os: ubuntu-16.04,   r: 'devel', rspm: "https://packagemanager.rstudio.com/cran/__linux__/xenial/latest", http-user-agent: "R/4.0.0 (ubuntu-16.04) R (4.0.0 x86_64-pc-linux-gnu x86_64 linux-gnu) on GitHub Actions" }
-          - {os: ubuntu-16.04,   r: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/xenial/latest"}
-          - {os: ubuntu-16.04,   r: 'oldrel',  rspm: "https://packagemanager.rstudio.com/cran/__linux__/xenial/latest"}
-          - {os: ubuntu-16.04,   r: '3.5',     rspm: "https://packagemanager.rstudio.com/cran/__linux__/xenial/latest"}
-          - {os: ubuntu-16.04,   r: '3.4',     rspm: "https://packagemanager.rstudio.com/cran/__linux__/xenial/latest"}
-          - {os: ubuntu-16.04,   r: '3.3',     rspm: "https://packagemanager.rstudio.com/cran/__linux__/xenial/latest"}
+          - {os: ubuntu-latest,   r: 'devel', http-user-agent: 'release'}
+          - {os: ubuntu-latest,   r: 'release'}
+          - {os: ubuntu-latest,   r: 'oldrel-1'}
+          - {os: ubuntu-latest,   r: 'oldrel-2'}
+          - {os: ubuntu-latest,   r: 'oldrel-3'}
+          - {os: ubuntu-latest,   r: 'oldrel-4'}
 
     env:
-      R_REMOTES_NO_ERRORS_FROM_WARNINGS: true
-      RSPM: ${{ matrix.config.rspm }}
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
+      R_KEEP_PKG_SOURCE: yes
 
     steps:
       - uses: actions/checkout@v2
 
-      - uses: r-lib/actions/setup-r@master
+      - uses: r-lib/actions/setup-pandoc@v2
+
+      - uses: r-lib/actions/setup-r@v2
         with:
           r-version: ${{ matrix.config.r }}
           http-user-agent: ${{ matrix.config.http-user-agent }}
+          use-public-rspm: true
 
-      - uses: r-lib/actions/setup-pandoc@master
-
-      - name: Query dependencies
-        run: |
-          install.packages('remotes')
-          saveRDS(remotes::dev_package_deps(dependencies = TRUE), ".github/depends.Rds", version = 2)
-          writeLines(sprintf("R-%i.%i", getRversion()$major, getRversion()$minor), ".github/R-version")
-        shell: Rscript {0}
-
-      - name: Cache R packages
-        if: runner.os != 'Windows'
-        uses: actions/cache@v2
+      - uses: r-lib/actions/setup-r-dependencies@v2
         with:
-          path: ${{ env.R_LIBS_USER }}
-          key: ${{ runner.os }}-${{ hashFiles('.github/R-version') }}-1-${{ hashFiles('.github/depends.Rds') }}
-          restore-keys: ${{ runner.os }}-${{ hashFiles('.github/R-version') }}-1-
-
-      - name: Install system dependencies
-        if: runner.os == 'Linux'
-        run: |
-          while read -r cmd
-          do
-            eval sudo $cmd
-          done < <(Rscript -e 'writeLines(remotes::system_requirements("ubuntu", "16.04"))')
-
-      - name: Install dependencies
-        run: |
-          remotes::install_deps(dependencies = TRUE)
-          remotes::install_cran("rcmdcheck")
-        shell: Rscript {0}
-
-      - name: Session info
-        run: |
-          options(width = 100)
-          pkgs <- installed.packages()[, "Package"]
-          sessioninfo::session_info(pkgs, include_base = TRUE)
-        shell: Rscript {0}
-
-      - name: Check
-        env:
-          _R_CHECK_CRAN_INCOMING_: false
-        run: rcmdcheck::rcmdcheck(args = c("--no-manual", "--as-cran"), error_on = "warning", check_dir = "check")
-        shell: Rscript {0}
-
-      - name: Show testthat output
-        if: always()
-        run: find check -name 'testthat.Rout*' -exec cat '{}' \; || true
-        shell: bash
+          extra-packages: any::rcmdcheck
+          needs: check
 
-      - name: Upload check results
-        if: failure()
-        uses: actions/upload-artifact@main
+      - uses: r-lib/actions/check-r-package@v2
         with:
-          name: ${{ runner.os }}-r${{ matrix.config.r }}-results
-          path: check
+          upload-snapshots: true
diff --git a/DESCRIPTION b/DESCRIPTION
index a9e269a4..ba659563 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: htmlwidgets
 Type: Package
 Title: HTML Widgets for R
-Version: 1.5.4.9000
+Version: 1.5.4.9001
 Authors@R: c(
     person("Ramnath", "Vaidyanathan", role = c("aut", "cph")),
     person("Yihui", "Xie", role = c("aut")),
@@ -19,7 +19,7 @@ License: MIT + file LICENSE
 VignetteBuilder: knitr
 Imports:
     grDevices,
-    htmltools (>= 0.3),
+    htmltools (>= 0.5.3.9001),
     jsonlite (>= 0.9.16),
     yaml
 Suggests:
@@ -30,3 +30,6 @@ Enhances: shiny (>= 1.1)
 URL: https://github.com/ramnathv/htmlwidgets
 BugReports: https://github.com/ramnathv/htmlwidgets/issues
 RoxygenNote: 7.2.1
+Encoding: UTF-8
+Remotes:
+    rstudio/htmltools
diff --git a/NEWS.md b/NEWS.md
index 5208261b..3feb521b 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,9 +1,12 @@
 htmlwidgets 1.5.4.9000
 -------------------------------------------------------
 
-### Breaking change
+### Potentially breaking changes
 
-* `shinyWidgetOutput()`'s `reportSize` argument now defaults to `TRUE`. This way, calling `shiny::getCurrentOutputInfo()` inside a `shinyRenderWidget()` context will report the current height and width of the widget. 
+* `shinyWidgetOutput()` and `sizingPolicy()` both gain a new `fill` parameter. When `TRUE` (the default), the widget's container element is allowed to grow/shrink to fit it's parent container so long as that parent is opinionated about its height and has been marked with `htmltools::bindFillRole(x, container = TRUE)`. (#442)
+  * The primary motivation for this is to allow widgets to grow/shrink by default [inside `bslib::card_body_fill()`](https://rstudio.github.io/bslib/articles/cards.html#responsive-sizing)
+  * Widgets that aren't designed to fill their container in this way should consider setting `sizingPolicy(fill = FALSE)`/`shinyWidgetOutput(fill = FALSE)` and/or allowing users to customize these settings (i.e., add a `fill` argument to the `customWidgetOutput()` function signature).
+* `shinyWidgetOutput()`'s `reportSize` argument now defaults to `TRUE`. This way, calling `shiny::getCurrentOutputInfo()` inside a `shinyRenderWidget()` context will report the current height and width of the widget.
 
 ### Improvements
 
diff --git a/R/htmlwidgets.R b/R/htmlwidgets.R
index 28a09fbf..fcb32c4a 100644
--- a/R/htmlwidgets.R
+++ b/R/htmlwidgets.R
@@ -170,62 +170,49 @@ addHook <- function(x, hookName, jsCode, data = NULL) {
 
 toHTML <- function(x, standalone = FALSE, knitrOptions = NULL) {
 
+  x$id <- x$elementId %||% paste("htmlwidget", createWidgetId(), sep = "-")
+
   sizeInfo <- resolveSizing(x, x$sizingPolicy, standalone = standalone, knitrOptions = knitrOptions)
 
-  if (!is.null(x$elementId))
-    id <- x$elementId
-  else
-    id <- paste("htmlwidget", createWidgetId(), sep="-")
+  name <- class(x)[1]
+  package <- attr(x, "package")
 
-  w <- validateCssUnit(sizeInfo$width)
-  h <- validateCssUnit(sizeInfo$height)
+  html <- widget_html(
+    name, package, id = x$id,
+    style = css(
+      width = validateCssUnit(sizeInfo$width),
+      height = validateCssUnit(sizeInfo$height)
+    ),
+    class = paste(name, "html-widget"),
+    width = sizeInfo$width,
+    height = sizeInfo$height
+  )
 
-  # create a style attribute for the width and height
-  style <- paste(
-    "width:", w, ";",
-    "height:", h, ";",
-    sep = "")
+  html <- bindFillRole(html, item = sizeInfo$fill)
 
-  x$id <- id
+  html <- tagList(x$append, html, x$prepend)
 
-  container <- if (isTRUE(standalone)) {
-    function(x) {
-      div(id="htmlwidget_container", x)
-    }
-  } else {
-    identity
+  if (isTRUE(standalone)) {
+    html <- div(id = "htmlwidget_container", html)
   }
 
-  html <- htmltools::tagList(
-    container(
-      htmltools::tagList(
-        x$prepend,
-        widget_html(
-          name = class(x)[1],
-          package = attr(x, "package"),
-          id = id,
-          style = style,
-          class = paste(class(x)[1], "html-widget"),
-          width = sizeInfo$width,
-          height = sizeInfo$height
-        ),
-        x$append
-      )
-    ),
-    widget_data(x, id),
+  html <- tagList(
+    html, widget_data(x, x$id),
     if (!is.null(sizeInfo$runtime)) {
-      tags$script(type="application/htmlwidget-sizing", `data-for` = id,
+      tags$script(
+        type = "application/htmlwidget-sizing",
+        `data-for` = x$id,
         toJSON(sizeInfo$runtime)
       )
     }
   )
-  html <- htmltools::attachDependencies(html,
-    c(widget_dependencies(class(x)[1], attr(x, 'package')),
-      x$dependencies)
-  )
 
-  htmltools::browsable(html)
+  deps <- c(
+    widget_dependencies(name, package),
+    x$dependencies
+  )
 
+  browsable(attachDependencies(html, deps, append = TRUE))
 }
 
 lookup_func <- function(name, package) {
@@ -263,7 +250,7 @@ lookup_widget_html_method <- function(name, package) {
   list(fn = widget_html.default, name = "widget_html.default", legacy = FALSE)
 }
 
-widget_html <- function (name, package, id, style, class, inline = FALSE, ...) {
+widget_html <- function(name, package, id, style, class, inline = FALSE, ...) {
 
   fn_info <- lookup_widget_html_method(name, package)
 
@@ -432,11 +419,11 @@ createWidget <- function(name,
 #'
 #' @param outputId output variable to read from
 #' @param name Name of widget to create output binding for
-#' @param width,height Must be a valid CSS unit (like \code{"100\%"},
-#'   \code{"400px"}, \code{"auto"}) or a number, which will be coerced to a
-#'   string and have \code{"px"} appended.
-#' @param package Package containing widget (defaults to \code{name})
-#' @param inline use an inline (\code{span()}) or block container (\code{div()})
+#' @param width,height Must be a valid CSS unit (like `"100%"`,
+#'   `"400px"`, `"auto"`) or a number, which will be coerced to a
+#'   string and have `"px"` appended.
+#' @param package Package containing widget (defaults to `name`)
+#' @param inline use an inline (`span()`) or block container (`div()`)
 #' for the output
 #' @param outputFunction Shiny output function corresponding to this render
 #'   function.
@@ -445,12 +432,17 @@ createWidget <- function(name,
 #' @param reportTheme Should the widget's container styles (e.g., colors and fonts)
 #' be reported in the shiny session's client data?
 #' @param expr An expression that generates an HTML widget (or a
-#'   \href{https://rstudio.github.io/promises/}{promise} of an HTML widget).
-#' @param env The environment in which to evaluate \code{expr}.
-#' @param quoted Is \code{expr} a quoted expression (with \code{quote()})? This
+#'   [promise](https://rstudio.github.io/promises/) of an HTML widget).
+#' @param env The environment in which to evaluate `expr`.
+#' @param quoted Is `expr` a quoted expression (with `quote()`)? This
 #'   is useful if you want to save an expression in a variable.
 #' @param cacheHint Extra information to use for optional caching using
-#'   \code{shiny::bindCache()}.
+#'   `shiny::bindCache()`.
+#' @param fill whether or not the returned tag should be treated as a fill item,
+#'   meaning that its `height` is allowed to grow/shrink to fit a fill container
+#'   with an opinionated height (see [htmltools::bindFillRole()] for more).
+#'   Examples of fill containers include `bslib::card()` and
+#'   `bslib::card_body_fill()`.
 #'
 #' @return An output or render function that enables the use of the widget
 #'   within Shiny applications.
@@ -473,8 +465,10 @@ createWidget <- function(name,
 #' @name htmlwidgets-shiny
 #'
 #' @export
+#' @md
 shinyWidgetOutput <- function(outputId, name, width, height, package = name,
-                              inline = FALSE, reportSize = TRUE, reportTheme = FALSE) {
+                              inline = FALSE, reportSize = TRUE, reportTheme = FALSE,
+                              fill = !inline) {
 
   # Theme reporting requires this shiny feature
   # https://github.com/rstudio/shiny/pull/2740/files
@@ -482,26 +476,29 @@ shinyWidgetOutput <- function(outputId, name, width, height, package = name,
     message("`reportTheme = TRUE` requires shiny v.1.4.0.9003 or higher. Consider upgrading shiny.")
   }
 
-  # generate html
-  html <- htmltools::tagList(
-    widget_html(
-      name, package, id = outputId,
-      class = paste0(
-        name, " html-widget html-widget-output",
-        if (reportSize) " shiny-report-size",
-        if (reportTheme) " shiny-report-theme"
-      ),
-      style = sprintf("width:%s; height:%s; %s",
-        htmltools::validateCssUnit(width),
-        htmltools::validateCssUnit(height),
-        if (inline) "display: inline-block;" else ""
-      ), width = width, height = height
+  tag <- widget_html(
+    name, package, id = outputId,
+    class = paste0(
+      name, " html-widget html-widget-output",
+      if (reportSize) " shiny-report-size",
+      if (reportTheme) " shiny-report-theme"
+    ),
+    style = css(
+      width = validateCssUnit(width),
+      height = validateCssUnit(height),
+      display = if (inline) "inline-block"
     )
   )
 
-  # attach dependencies
-  dependencies = widget_dependencies(name, package)
-  htmltools::attachDependencies(html, dependencies)
+  tag <- bindFillRole(tag, item = fill)
+
+  # Adds an additional and unnecessary tagList() container to the return value...
+  # I'd love remove it, but lets keep it for backwards-compatibility
+  tag <- tagList(tag)
+
+  attachDependencies(
+    tag, widget_dependencies(name, package), append = TRUE
+  )
 }
 
 
diff --git a/R/sizing.R b/R/sizing.R
index 7b059409..348104b1 100644
--- a/R/sizing.R
+++ b/R/sizing.R
@@ -10,7 +10,7 @@
 #' @param defaultWidth The default width used to display the widget. This
 #'   parameter specifies the default width for viewing in all contexts (browser,
 #'   viewer, and knitr) unless it is specifically overridden with e.g.
-#'   \code{browser.defaultWidth}.
+#'   `browser.defaultWidth`.
 #' @param viewer.defaultWidth The default width used to display the widget
 #'   within the RStudio Viewer.
 #' @param browser.defaultWidth The default width used to display the widget
@@ -29,28 +29,33 @@
 #'   within documents generated by knitr (e.g. R Markdown).
 #' @param padding Padding around the widget (in pixels). This parameter
 #'   specifies the padding for viewing in all contexts (browser and viewer)
-#'   unless it is specifically overriden by e.g. \code{browser.padding}.
+#'   unless it is specifically overriden by e.g. `browser.padding`.
 #' @param browser.padding Padding around the widget when displayed in a
 #'   standalone browser (defaults to 40 pixels).
 #' @param viewer.padding Padding around the widget when displayed in the RStudio
 #'   Viewer (defaults to 15 pixels).
 #' @param viewer.fill When displayed in the RStudio Viewer, automatically size
-#'   the widget to the viewer dimensions (note that \code{viewer.padding} is
-#'   still applied). Default to \code{TRUE}.
+#'   the widget to the viewer dimensions (note that `viewer.padding` is
+#'   still applied). Default to `TRUE`.
 #' @param browser.fill When displayed in a standalone web browser, automatically
-#'   size the widget to the browser dimensions (note that \code{browser.padding}
-#'   is still applied). Defaults to \code{FALSE}.
+#'   size the widget to the browser dimensions (note that `browser.padding`
+#'   is still applied). Defaults to `FALSE`.
 #' @param browser.external When displaying in a browser, always use an external
-#'   browser (via \code{browseURL()}). Defaults to \code{FALSE}, which will
+#'   browser (via [browseURL()]). Defaults to `FALSE``, which will
 #'   result in the use of an internal browser within RStudio v1.1 and higher.
 #' @param viewer.paneHeight Request that the RStudio Viewer be forced to a
 #'   specific height when displaying this widget.
 #' @param viewer.suppress Never display the widget within the RStudio Viewer
 #'   (useful for widgets that require a large amount of space for rendering).
-#'   Defaults to \code{FALSE}.
+#'   Defaults to `FALSE`.
 #' @param knitr.figure Apply the default knitr fig.width and fig.height to the
 #'   widget when it's rendered within R Markdown documents. Defaults to
-#'   \code{TRUE}.
+#'   `TRUE`.
+#' @param fill Whether or not the widget's container should be treated as a fill
+#'   item, meaning that its `height` is allowed to grow/shrink to fit a fill
+#'   container with an opinionated height (see [htmltools::bindFillRole()] for
+#'   more). Examples of fill containers include `bslib::card()` and
+#'   `bslib::card_body_fill()`.
 #'
 #' @return A widget sizing policy
 #'
@@ -63,20 +68,20 @@
 #' based on the default size of figures in the document.
 #'
 #' You might need to change the default behavior if your widget is extremely
-#' large. In this case you might specify \code{viewer.suppress = TRUE} and
-#' \code{knitr.figure = FALSE} as well provide for a larger default width and
+#' large. In this case you might specify `viewer.suppress = TRUE` and
+#' `knitr.figure = FALSE` as well provide for a larger default width and
 #' height for knitr.
 #'
 #' You also might need to change the default behavior if you widget already
-#' incorporates padding. In this case you might specify \code{viewer.padding =
-#' 0}.
+#' incorporates padding. In this case you might specify `viewer.padding = 0`.
 #'
 #' For additional details on widget sizing:
 #'
-#' \code{vignette("develop_sizing", package = "htmlwidgets")}
+#' `vignette("develop_sizing", package = "htmlwidgets")`
 #'
 #'
 #' @export
+#' @md
 sizingPolicy <- function(
   defaultWidth = NULL, defaultHeight = NULL, padding = NULL,
   viewer.defaultWidth = NULL, viewer.defaultHeight = NULL,
@@ -85,12 +90,13 @@ sizingPolicy <- function(
   browser.defaultWidth = NULL, browser.defaultHeight = NULL,
   browser.padding = NULL, browser.fill = FALSE, browser.external = FALSE,
   knitr.defaultWidth = NULL, knitr.defaultHeight = NULL,
-  knitr.figure = TRUE) {
+  knitr.figure = TRUE, fill = NULL) {
 
   list(
     defaultWidth = defaultWidth,
     defaultHeight = defaultHeight,
     padding = padding,
+    fill = fill,
     viewer = list(
       defaultWidth = viewer.defaultWidth,
       defaultHeight = viewer.defaultHeight,
@@ -185,9 +191,11 @@ DEFAULT_PADDING_VIEWER <- 15
 #' @keywords internal
 #' @noRd
 resolveSizing <- function(x, sp, standalone, knitrOptions = NULL) {
+  userSized <- !is.null(x$width) || !is.null(x$height)
+  viewerScopes <- list(sp$viewer, sp)
+  viewerFill <- !userSized && any_prop(viewerScopes, "fill") %||% TRUE
+
   if (isTRUE(standalone)) {
-    userSized <- !is.null(x$width) || !is.null(x$height)
-    viewerScopes <- list(sp$viewer, sp)
     browserScopes <- list(sp$browser, sp)
     # Precompute the width, height, padding, and fill for each scenario.
     return(list(
@@ -196,7 +204,7 @@ resolveSizing <- function(x, sp, standalone, knitrOptions = NULL) {
           width = x$width %||% any_prop(viewerScopes, "defaultWidth") %||% DEFAULT_WIDTH_VIEWER,
           height = x$height %||% any_prop(viewerScopes, "defaultHeight") %||% DEFAULT_HEIGHT_VIEWER,
           padding = any_prop(viewerScopes, "padding") %||% DEFAULT_PADDING_VIEWER,
-          fill = !userSized && any_prop(viewerScopes, "fill") %||% TRUE
+          fill = viewerFill
         ),
         browser = list(
           width = x$width %||% any_prop(browserScopes, "defaultWidth") %||% DEFAULT_WIDTH,
@@ -206,31 +214,36 @@ resolveSizing <- function(x, sp, standalone, knitrOptions = NULL) {
         )
       ),
       width = x$width %||% prop(sp, "defaultWidth") %||% DEFAULT_WIDTH,
-      height = x$height %||% prop(sp, "defaultHeight") %||% DEFAULT_HEIGHT
+      height = x$height %||% prop(sp, "defaultHeight") %||% DEFAULT_HEIGHT,
+      fill = prop(sp, "fill") %||% viewerFill
     ))
-  } else if (!is.null(knitrOptions)) {
+  }
+
+  if (!is.null(knitrOptions)) {
     knitrScopes <- list(sp$knitr, sp)
     isFigure <- any_prop(knitrScopes, "figure")
-    # flexdashboard actually adds on another fig.width for intelligent sizing of static 
+    # flexdashboard actually adds on another fig.width for intelligent sizing of static
     # figures in desktop/mobile mode
     # https://github.com/rstudio/flexdashboard/blob/02207b7/R/flex_dashboard.R#L262
-    # flexdashboard should really only be doing this for static plots, but we make sure 
-    # to just take the first (desktop) sizing to make this "just work" for flexdashboard 
-    # (or really anyone else that provides a vector of widths/heights for a widget by 
+    # flexdashboard should really only be doing this for static plots, but we make sure
+    # to just take the first (desktop) sizing to make this "just work" for flexdashboard
+    # (or really anyone else that provides a vector of widths/heights for a widget by
     # just taking the 1st value)
     figWidth <- if (isFigure) knitrOptions$out.width.px[[1L]] else NULL
     figHeight <- if (isFigure) knitrOptions$out.height.px[[1L]] else NULL
     # Compute the width and height
     return(list(
       width = x$width %||% figWidth %||% any_prop(knitrScopes, "defaultWidth") %||% DEFAULT_WIDTH,
-      height = x$height %||% figHeight %||% any_prop(knitrScopes, "defaultHeight") %||% DEFAULT_HEIGHT
-    ))
-  } else {
-    # Some non-knitr, non-print scenario.
-    # Just resolve the width/height vs. defaultWidth/defaultHeight
-    return(list(
-      width = x$width %||% prop(sp, "defaultWidth") %||% DEFAULT_WIDTH,
-      height = x$height %||% prop(sp, "defaultHeight") %||% DEFAULT_HEIGHT
+      height = x$height %||% figHeight %||% any_prop(knitrScopes, "defaultHeight") %||% DEFAULT_HEIGHT,
+      fill = prop(knitrScopes, "fill") %||% viewerFill
     ))
   }
+
+  # Some non-knitr, non-print scenario.
+  # Just resolve the width/height vs. defaultWidth/defaultHeight
+  list(
+    width = x$width %||% prop(sp, "defaultWidth") %||% DEFAULT_WIDTH,
+    height = x$height %||% prop(sp, "defaultHeight") %||% DEFAULT_HEIGHT,
+    fill = prop(sp, "fill") %||% viewerFill
+  )
 }
diff --git a/man/htmlwidgets-shiny.Rd b/man/htmlwidgets-shiny.Rd
index ecc60d3e..01873ab1 100644
--- a/man/htmlwidgets-shiny.Rd
+++ b/man/htmlwidgets-shiny.Rd
@@ -14,7 +14,8 @@ shinyWidgetOutput(
   package = name,
   inline = FALSE,
   reportSize = TRUE,
-  reportTheme = FALSE
+  reportTheme = FALSE,
+  fill = !inline
 )
 
 shinyRenderWidget(expr, outputFunction, env, quoted, cacheHint = "auto")
@@ -39,6 +40,12 @@ shiny session's client data?}
 \item{reportTheme}{Should the widget's container styles (e.g., colors and fonts)
 be reported in the shiny session's client data?}
 
+\item{fill}{whether or not the returned tag should be treated as a fill item,
+meaning that its \code{height} is allowed to grow/shrink to fit a fill container
+with an opinionated height (see \code{\link[htmltools:bindFillRole]{htmltools::bindFillRole()}} for more).
+Examples of fill containers include \code{bslib::card()} and
+\code{bslib::card_body_fill()}.}
+
 \item{expr}{An expression that generates an HTML widget (or a
 \href{https://rstudio.github.io/promises/}{promise} of an HTML widget).}
 
@@ -55,7 +62,7 @@ is useful if you want to save an expression in a variable.}
 }
 \value{
 An output or render function that enables the use of the widget
-  within Shiny applications.
+within Shiny applications.
 }
 \description{
 Helpers to create output and render functions for using HTML widgets within
@@ -63,8 +70,8 @@ Shiny applications and interactive Rmd documents.
 }
 \details{
 These functions are delegated to from within your widgets own shiny
-  output and render functions. The delegation is boilerplate and always works
-  the same for all widgets (see example below).
+output and render functions. The delegation is boilerplate and always works
+the same for all widgets (see example below).
 }
 \examples{
 # shiny output binding for a widget named 'foo'
diff --git a/man/sizingPolicy.Rd b/man/sizingPolicy.Rd
index fcaef019..e5d3588f 100644
--- a/man/sizingPolicy.Rd
+++ b/man/sizingPolicy.Rd
@@ -21,7 +21,8 @@ sizingPolicy(
   browser.external = FALSE,
   knitr.defaultWidth = NULL,
   knitr.defaultHeight = NULL,
-  knitr.figure = TRUE
+  knitr.figure = TRUE,
+  fill = NULL
 )
 }
 \arguments{
@@ -73,7 +74,7 @@ size the widget to the browser dimensions (note that \code{browser.padding}
 is still applied). Defaults to \code{FALSE}.}
 
 \item{browser.external}{When displaying in a browser, always use an external
-browser (via \code{browseURL()}). Defaults to \code{FALSE}, which will
+browser (via \code{\link[=browseURL]{browseURL()}}). Defaults to `FALSE``, which will
 result in the use of an internal browser within RStudio v1.1 and higher.}
 
 \item{knitr.defaultWidth}{The default width used to display the widget within
@@ -85,6 +86,12 @@ within documents generated by knitr (e.g. R Markdown).}
 \item{knitr.figure}{Apply the default knitr fig.width and fig.height to the
 widget when it's rendered within R Markdown documents. Defaults to
 \code{TRUE}.}
+
+\item{fill}{Whether or not the widget's container should be treated as a fill
+item, meaning that its \code{height} is allowed to grow/shrink to fit a fill
+container with an opinionated height (see \code{\link[htmltools:bindFillRole]{htmltools::bindFillRole()}} for
+more). Examples of fill containers include \code{bslib::card()} and
+\code{bslib::card_body_fill()}.}
 }
 \value{
 A widget sizing policy
@@ -110,8 +117,7 @@ large. In this case you might specify \code{viewer.suppress = TRUE} and
 height for knitr.
 
 You also might need to change the default behavior if you widget already
-incorporates padding. In this case you might specify \code{viewer.padding =
-0}.
+incorporates padding. In this case you might specify \code{viewer.padding = 0}.
 
 For additional details on widget sizing: