diff --git a/DESCRIPTION b/DESCRIPTION
index a6505e2a4..40a31d936 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Type: Package
 Package: insight
 Title: Easy Access to Model Information for Various Model Objects
-Version: 1.4.2.4
+Version: 1.4.2.5
 Authors@R:
     c(person(given = "Daniel",
              family = "Lüdecke",
diff --git a/NEWS.md b/NEWS.md
index 35c4629b3..1ffc23147 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -11,6 +11,12 @@
 * Better formatting for p-values-columns from equivalence tests from other
   packages.
 
+* `format_value()`, `format_number()`, and `export_table()` gain a `big_mark`
+  argument to format numbers with thousands separators (e.g., `1,234,567.89` or
+  `1 234 567.89`). This makes large numbers more readable in tables and formatted
+  output. When `big_mark` is provided, scientific notation is suppressed for
+  large numbers to show the full value with separators.
+
 ## Bug fixes
 
 * Fix CRAN check failures.
diff --git a/R/export_table.R b/R/export_table.R
index 089d3a16e..466d50dd4 100644
--- a/R/export_table.R
+++ b/R/export_table.R
@@ -207,6 +207,7 @@ export_table <- function(x,
                          align = NULL,
                          by = NULL,
                          zap_small = FALSE,
+                         big_mark = NULL,
                          table_width = "auto",
                          remove_duplicates = FALSE,
                          row_groups = NULL,
@@ -267,6 +268,7 @@ export_table <- function(x,
     align = align,
     group_by = by,
     zap_small = zap_small,
+    big_mark = big_mark,
     empty_line = empty_line,
     indent_groups = indent_groups,
     row_groups = row_groups,
@@ -511,6 +513,7 @@ print.insight_table <- function(x, ...) {
                           align = NULL,
                           group_by = NULL,
                           zap_small = FALSE,
+                          big_mark = NULL,
                           empty_line = NULL,
                           indent_groups = NULL,
                           row_groups = NULL,
@@ -549,7 +552,8 @@ print.insight_table <- function(x, ...) {
     if (is.numeric(i)) {
       out <- format_value(i,
         digits = digits, protect_integers = protect_integers,
-        missing = missing, width = col_width, zap_small = zap_small
+        missing = missing, width = col_width, zap_small = zap_small,
+        big_mark = big_mark
       )
     } else {
       out <- i
@@ -1386,15 +1390,16 @@ print.insight_table <- function(x, ...) {
 # --------------------------------------------------------
 
 .format_html_table <- function(
-    final,
-    caption = NULL,
-    subtitle = NULL,
-    footer = NULL,
-    align = "center",
-    group_by = NULL,
-    row_groups = NULL,
-    column_groups = NULL,
-    ...) {
+  final,
+  caption = NULL,
+  subtitle = NULL,
+  footer = NULL,
+  align = "center",
+  group_by = NULL,
+  row_groups = NULL,
+  column_groups = NULL,
+  ...
+) {
   check_if_installed("gt")
 
   if (is.null(align)) {
diff --git a/R/format_value.R b/R/format_value.R
index 985107fbb..eaa385e15 100644
--- a/R/format_value.R
+++ b/R/format_value.R
@@ -36,6 +36,9 @@
 #'   `"parens"` to wrap the number in parentheses.
 #' @param decimal_point Character string containing a single character that
 #'   is used as decimal point in output conversions.
+#' @param big_mark Character used as thousands separator. If `NULL` (default),
+#'   no thousands separator is used. Use `","` for comma separator or `" "`
+#'   for space separator.
 #' @param ... Arguments passed to or from other methods.
 #'
 #'
@@ -52,6 +55,8 @@
 #' format_value(c(0.0045, 0.12, 0.34), digits = "scientific2")
 #' format_value(c(0.045, 0.12, 0.34), lead_zero = FALSE)
 #' format_value(c(0.0045, 0.12, 0.34), decimal_point = ",")
+#' format_value(c(1234567.89, 1234.56), big_mark = ",")
+#' format_value(c(1234567.89, 1234.56), big_mark = " ")
 #'
 #' # default
 #' format_value(c(0.0045, 0.123, 0.345))
@@ -73,18 +78,21 @@ format_value <- function(x, ...) {
 
 #' @rdname format_value
 #' @export
-format_value.data.frame <- function(x,
-                                    digits = 2,
-                                    protect_integers = FALSE,
-                                    missing = "",
-                                    width = NULL,
-                                    as_percent = FALSE,
-                                    zap_small = FALSE,
-                                    lead_zero = TRUE,
-                                    style_positive = "none",
-                                    style_negative = "hyphen",
-                                    decimal_point = getOption("OutDec"),
-                                    ...) {
+format_value.data.frame <- function(
+  x,
+  digits = 2,
+  protect_integers = FALSE,
+  missing = "",
+  width = NULL,
+  as_percent = FALSE,
+  zap_small = FALSE,
+  lead_zero = TRUE,
+  style_positive = "none",
+  style_negative = "hyphen",
+  decimal_point = getOption("OutDec"),
+  big_mark = NULL,
+  ...
+) {
   as.data.frame(sapply(
     x,
     format_value,
@@ -98,6 +106,7 @@ format_value.data.frame <- function(x,
     style_positive = style_positive,
     style_negative = style_negative,
     decimal_point = decimal_point,
+    big_mark = big_mark,
     simplify = FALSE
   ))
 }
@@ -105,18 +114,21 @@ format_value.data.frame <- function(x,
 
 #' @rdname format_value
 #' @export
-format_value.numeric <- function(x,
-                                 digits = 2,
-                                 protect_integers = FALSE,
-                                 missing = "",
-                                 width = NULL,
-                                 as_percent = FALSE,
-                                 zap_small = FALSE,
-                                 lead_zero = TRUE,
-                                 style_positive = "none",
-                                 style_negative = "hyphen",
-                                 decimal_point = getOption("OutDec"),
-                                 ...) {
+format_value.numeric <- function(
+  x,
+  digits = 2,
+  protect_integers = FALSE,
+  missing = "",
+  width = NULL,
+  as_percent = FALSE,
+  zap_small = FALSE,
+  lead_zero = TRUE,
+  style_positive = "none",
+  style_negative = "hyphen",
+  decimal_point = getOption("OutDec"),
+  big_mark = NULL,
+  ...
+) {
   # check input
   style_positive <- validate_argument(style_positive, c("none", "plus", "space"))
   style_negative <- validate_argument(style_negative, c("hyphen", "minus", "parens"))
@@ -129,6 +141,7 @@ format_value.numeric <- function(x,
       .width = width,
       .as_percent = as_percent,
       .zap_small = zap_small,
+      .big_mark = big_mark,
       ...
     )
   } else {
@@ -139,6 +152,7 @@ format_value.numeric <- function(x,
       .width = width,
       .as_percent = as_percent,
       .zap_small = zap_small,
+      .big_mark = big_mark,
       ...
     )
   }
@@ -205,12 +219,16 @@ format_percent <- function(x, ...) {
 }
 
 
-.format_value_unless_integer <- function(x,
-                                         digits = 2,
-                                         .missing = "",
-                                         .width = NULL,
-                                         .as_percent = FALSE,
-                                         .zap_small = FALSE, ...) {
+.format_value_unless_integer <- function(
+  x,
+  digits = 2,
+  .missing = "",
+  .width = NULL,
+  .as_percent = FALSE,
+  .zap_small = FALSE,
+  .big_mark = NULL,
+  ...
+) {
   x_nonmiss <- x[!is.na(x)]
   if (is.numeric(x) && !all(.is_integer(x_nonmiss))) {
     .format_value(
@@ -219,41 +237,66 @@ format_percent <- function(x, ...) {
       .missing = .missing,
       .width = .width,
       .as_percent = .as_percent,
-      .zap_small = .zap_small
+      .zap_small = .zap_small,
+      .big_mark = .big_mark
     )
   } else if (anyNA(x)) {
     .convert_missing(x, .missing)
   } else if (is.numeric(x) && all(.is_integer(x_nonmiss)) && !is.null(.width)) {
     format(x, justify = "right", width = .width)
   } else {
-    as.character(x)
+    # For integers, apply big_mark if requested
+    out <- as.character(x)
+    if (!is.null(.big_mark) && !identical(.big_mark, "")) {
+      needs_big_mark <- !is.na(out) & out != .missing
+      if (any(needs_big_mark)) {
+        out[needs_big_mark] <- prettyNum(
+          as.numeric(out[needs_big_mark]),
+          big.mark = .big_mark,
+          preserve.width = "none",
+          scientific = FALSE
+        )
+      }
+    }
+    out
   }
 }
 
 
-.format_value <- function(x,
-                          digits = 2,
-                          .missing = "",
-                          .width = NULL,
-                          .as_percent = FALSE,
-                          .zap_small = FALSE,
-                          ...) {
+.format_value <- function(
+  x,
+  digits = 2,
+  .missing = "",
+  .width = NULL,
+  .as_percent = FALSE,
+  .zap_small = FALSE,
+  .big_mark = NULL,
+  ...
+) {
   # proper character NA
-  if (is.na(.missing)) .missing <- NA_character_
+  if (is.na(.missing)) {
+    .missing <- NA_character_
+  }
 
   # sometimes, digits can be `NULL` - sanity check
   if (is.null(digits)) {
     digits <- 2
   }
 
+  use_big_mark <- !is.null(.big_mark) && !identical(.big_mark, "")
+
   if (is.numeric(x)) {
     if (isTRUE(.as_percent)) {
       need_sci <- (abs(100 * x) >= 1e+5 | (log10(abs(100 * x)) < -digits)) & x != 0
-      if (.zap_small) {
+      # When big_mark is provided, suppress scientific notation for percentages too
+      if (.zap_small || use_big_mark) {
         x <- ifelse(is.na(x), .missing, sprintf("%.*f%%", digits, 100 * x))
       } else {
-        x <- ifelse(is.na(x), .missing,
-          ifelse(need_sci, # nolint
+        x <- ifelse(
+          is.na(x),
+          .missing,
+          ifelse(
+            need_sci,
             sprintf("%.*e%%", digits, 100 * x),
             sprintf("%.*f%%", digits, 100 * x)
           )
@@ -266,7 +309,9 @@ format_percent <- function(x, ...) {
           5
         }
       )
-      if (is.na(digits)) digits <- 5
+      if (is.na(digits)) {
+        digits <- 5
+      }
       x <- sprintf("%.*e", digits, x)
     } else if (is.character(digits) && grepl("signif", digits, fixed = TRUE)) {
       digits <- tryCatch(
@@ -275,21 +320,58 @@ format_percent <- function(x, ...) {
           NA
         }
       )
-      if (is.na(digits)) digits <- 3
+      if (is.na(digits)) {
+        digits <- 3
+      }
       x <- as.character(signif(x, digits))
     } else {
+      # When big_mark is provided, suppress scientific notation for large numbers
+      # since the user wants to see the full number with thousands separators
       need_sci <- (abs(x) >= 1e+5 | (log10(abs(x)) < -digits)) & x != 0
-      if (.zap_small) {
+      if (.zap_small || use_big_mark) {
         x <- ifelse(is.na(x), .missing, sprintf("%.*f", digits, x))
       } else {
-        x <- ifelse(is.na(x), .missing,
-          ifelse(need_sci, # nolint
+        x <- ifelse(
+          is.na(x),
+          .missing,
+          ifelse(
+            need_sci, # nolint
             sprintf("%.*e", digits, x),
             sprintf("%.*f", digits, x)
           )
         )
       }
     }
+
+    # Apply thousands separator if requested
+    # Only apply to non-scientific notation values
+    if (!is.null(.big_mark) && !identical(.big_mark, "") && is.character(x)) {
+      # Don't apply to scientific notation (contains 'e')
+      needs_big_mark <- !grepl("e", x, fixed = TRUE) & !is.na(x) & x != .missing
+      if (any(needs_big_mark)) {
+        # For percentages, we need to handle them specially
+        has_percent <- grepl("%", x, fixed = TRUE)
+
+        # Apply big_mark to non-percentage values directly
+        if (any(needs_big_mark & !has_percent)) {
+          x[needs_big_mark & !has_percent] <- prettyNum(
+            x[needs_big_mark & !has_percent],
+            big.mark = .big_mark,
+            preserve.width = "none"
+          )
+        }
+
+        # For percentages, extract the number, apply big_mark, then add % back
+        if (any(needs_big_mark & has_percent)) {
+          selector <- needs_big_mark & has_percent
+          num_parts <- gsub("%", "", x[selector], fixed = TRUE)
+          x[selector] <- paste0(
+            prettyNum(num_parts, big.mark = .big_mark, preserve.width = "none"),
+            "%"
+          )
+        }
+      }
+    }
   } else if (anyNA(x)) {
     x <- .convert_missing(x, .missing)
   }
diff --git a/R/get_predicted_bayesian.R b/R/get_predicted_bayesian.R
index 7f4476788..201d13ce0 100644
--- a/R/get_predicted_bayesian.R
+++ b/R/get_predicted_bayesian.R
@@ -4,16 +4,17 @@
 #' @rdname get_predicted
 #' @export
 get_predicted.stanreg <- function(
-    x,
-    data = NULL,
-    predict = "expectation",
-    iterations = NULL,
-    ci = NULL,
-    ci_method = NULL,
-    include_random = "default",
-    include_smooth = TRUE,
-    verbose = TRUE,
-    ...) {
+  x,
+  data = NULL,
+  predict = "expectation",
+  iterations = NULL,
+  ci = NULL,
+  ci_method = NULL,
+  include_random = "default",
+  include_smooth = TRUE,
+  verbose = TRUE,
+  ...
+) {
   check_if_installed("rstantools")
 
   if (is.null(ci_method)) {
diff --git a/R/n_obs.R b/R/n_obs.R
index cbe4d4236..f56aaff24 100644
--- a/R/n_obs.R
+++ b/R/n_obs.R
@@ -48,7 +48,8 @@ n_obs.default <- function(x, ...) {
     },
     error = function(e) {
       FALSE
-    })
+    }
+  )
 
   if (isTRUE(is_binomial)) {
     return(n_obs.glm(x, ...))
@@ -68,7 +69,8 @@ n_obs.glm <- function(x, disaggregate = FALSE, ...) {
     },
     error = function(e) {
       FALSE
-    })
+    }
+  )
 
   .nobs <- stats::nobs(x)
 
diff --git a/man/export_table.Rd b/man/export_table.Rd
index 3c0f97b33..c5426465a 100644
--- a/man/export_table.Rd
+++ b/man/export_table.Rd
@@ -23,6 +23,7 @@ export_table(
   align = NULL,
   by = NULL,
   zap_small = FALSE,
+  big_mark = NULL,
   table_width = "auto",
   remove_duplicates = FALSE,
   row_groups = NULL,
@@ -117,6 +118,10 @@ frames. See also \code{row_groups} to group rows in the printed output.}
 \code{digits} decimal places. If \code{FALSE}, values with more decimal
 places than \code{digits} are printed in scientific notation.}
 
+\item{big_mark}{Character used as thousands separator. If \code{NULL} (default),
+no thousands separator is used. Use \code{","} for comma separator or \code{" "}
+for space separator.}
+
 \item{table_width}{Numeric,\code{"auto"}, \code{NULL} or \code{Inf}, indicating the width of
 the complete table.
 \itemize{
diff --git a/man/format_value.Rd b/man/format_value.Rd
index bb06bdc59..5cff6abc6 100644
--- a/man/format_value.Rd
+++ b/man/format_value.Rd
@@ -21,6 +21,7 @@ format_value(x, ...)
   style_positive = "none",
   style_negative = "hyphen",
   decimal_point = getOption("OutDec"),
+  big_mark = NULL,
   ...
 )
 
@@ -36,6 +37,7 @@ format_value(x, ...)
   style_positive = "none",
   style_negative = "hyphen",
   decimal_point = getOption("OutDec"),
+  big_mark = NULL,
   ...
 )
 
@@ -84,6 +86,10 @@ May be \code{"hyphen"} (default), \code{"minus"} for a proper Unicode minus symb
 
 \item{decimal_point}{Character string containing a single character that
 is used as decimal point in output conversions.}
+
+\item{big_mark}{Character used as thousands separator. If \code{NULL} (default),
+no thousands separator is used. Use \code{","} for comma separator or \code{" "}
+for space separator.}
 }
 \value{
 A formatted string.
@@ -104,6 +110,8 @@ format_value(c(0.0045, 0.12, 0.34), digits = "scientific")
 format_value(c(0.0045, 0.12, 0.34), digits = "scientific2")
 format_value(c(0.045, 0.12, 0.34), lead_zero = FALSE)
 format_value(c(0.0045, 0.12, 0.34), decimal_point = ",")
+format_value(c(1234567.89, 1234.56), big_mark = ",")
+format_value(c(1234567.89, 1234.56), big_mark = " ")
 
 # default
 format_value(c(0.0045, 0.123, 0.345))
diff --git a/tests/testthat/test-betareg.R b/tests/testthat/test-betareg.R
index 0c7fe9239..584e4f0ff 100644
--- a/tests/testthat/test-betareg.R
+++ b/tests/testthat/test-betareg.R
@@ -1,4 +1,5 @@
 skip_if_not_installed("betareg")
+skip_if_not_installed("statmod")
 
 data("GasolineYield", package = "betareg")
 data("FoodExpenditure", package = "betareg")
diff --git a/tests/testthat/test-export_table.R b/tests/testthat/test-export_table.R
index 4a5ceb179..46f15cc41 100644
--- a/tests/testthat/test-export_table.R
+++ b/tests/testthat/test-export_table.R
@@ -13,15 +13,21 @@ test_that("export_table", {
 
 test_that("export_table", {
   out <- export_table(d, format = "md")
-  expect_equal(out, structure(
-    c(
-      "|      a|     b|", "|------:|-----:|",
-      "|   1.30|    ab|", "|   2.00|    cd|",
-      "| 543.00| abcde|"
+  expect_equal(
+    out,
+    structure(
+      c(
+        "|      a|     b|",
+        "|------:|-----:|",
+        "|   1.30|    ab|",
+        "|   2.00|    cd|",
+        "| 543.00| abcde|"
+      ),
+      format = "pipe",
+      class = c("knitr_kable", "character")
     ),
-    format = "pipe",
-    class = c("knitr_kable", "character")
-  ), ignore_attr = TRUE)
+    ignore_attr = TRUE
+  )
 })
 
 d <- data.frame(a = c(1.3, 2, 543), b = c("ab", "cd", "abcde"), stringsAsFactors = FALSE)
@@ -33,8 +39,13 @@ test_that("export_table", {
     out,
     structure(
       c(
-        "Table: Table Title", "", "|      a|     b|", "|------:|-----:|",
-        "|   1.30|    ab|", "|   2.00|    cd|", "| 543.00| abcde|"
+        "Table: Table Title",
+        "",
+        "|      a|     b|",
+        "|------:|-----:|",
+        "|   1.30|    ab|",
+        "|   2.00|    cd|",
+        "| 543.00| abcde|"
       ),
       format = "pipe",
       class = c("knitr_kable", "character")
@@ -52,8 +63,13 @@ test_that("export_table", {
     out,
     structure(
       c(
-        "Table: Table Title", "", "|      a|     b|", "|------:|-----:|",
-        "|   1.30|    ab|", "|   2.00|    cd|", "| 543.00| abcde|"
+        "Table: Table Title",
+        "",
+        "|      a|     b|",
+        "|------:|-----:|",
+        "|   1.30|    ab|",
+        "|   2.00|    cd|",
+        "| 543.00| abcde|"
       ),
       format = "pipe",
       class = c("knitr_kable", "character")
@@ -70,8 +86,13 @@ test_that("export_table", {
     out,
     structure(
       c(
-        "Table: Table Title", "", "|      a|     b|", "|------:|-----:|",
-        "|   1.30|    ab|", "|   2.00|    cd|", "| 543.00| abcde|"
+        "Table: Table Title",
+        "",
+        "|      a|     b|",
+        "|------:|-----:|",
+        "|   1.30|    ab|",
+        "|   2.00|    cd|",
+        "| 543.00| abcde|"
       ),
       format = "pipe",
       class = c("knitr_kable", "character")
@@ -90,9 +111,16 @@ test_that("export_table", {
     out,
     structure(
       c(
-        "Table: Table Title", "", "|      a|     b|", "|------:|-----:|",
-        "|   1.30|    ab|", "|   2.00|    cd|", "| 543.00| abcde|",
-        "first", "second", "third"
+        "Table: Table Title",
+        "",
+        "|      a|     b|",
+        "|------:|-----:|",
+        "|   1.30|    ab|",
+        "|   2.00|    cd|",
+        "| 543.00| abcde|",
+        "first",
+        "second",
+        "third"
       ),
       format = "pipe",
       class = c("knitr_kable", "character")
@@ -122,7 +150,10 @@ test_that("export_table, table_width", {
   lm1 <- lm(Sepal.Length ~ Species, data = iris)
   lm2 <- lm(Sepal.Length ~ Species + Petal.Length, data = iris)
   lm3 <- lm(Sepal.Length ~ Species * Petal.Length, data = iris)
-  lm6 <- lm5 <- lm4 <- lm(Sepal.Length ~ Species * Petal.Length + Petal.Width, data = iris)
+  lm6 <- lm5 <- lm4 <- lm(
+    Sepal.Length ~ Species * Petal.Length + Petal.Width,
+    data = iris
+  )
 
   tab <- parameters::compare_parameters(lm1, lm2, lm3, lm4, lm5, lm6)
   expect_snapshot(print(tab, ci_digits = 2, table_width = 80), variant = "windows")
@@ -149,7 +180,10 @@ test_that("export_table, table_width, no split", {
   lm1 <- lm(Sepal.Length ~ Species, data = iris)
   lm2 <- lm(Sepal.Length ~ Species + Petal.Length, data = iris)
   lm3 <- lm(Sepal.Length ~ Species * Petal.Length, data = iris)
-  lm6 <- lm5 <- lm4 <- lm(Sepal.Length ~ Species * Petal.Length + Petal.Width, data = iris)
+  lm6 <- lm5 <- lm4 <- lm(
+    Sepal.Length ~ Species * Petal.Length + Petal.Width,
+    data = iris
+  )
 
   tab <- parameters::compare_parameters(lm1, lm2, lm3, lm4, lm5, lm6)
   expect_snapshot(print(tab, table_width = NULL), variant = "windows")
@@ -162,24 +196,82 @@ test_that("export_table, table_width, remove duplicated empty lines", {
   out <- datawizard::data_codebook(efc)
   out$.row_id <- NULL
   expect_snapshot(print(export_table(out, table_width = 60, remove_duplicates = FALSE)))
-  expect_snapshot(print(export_table(out, table_width = 60, empty_line = "-", remove_duplicates = FALSE)))
-  expect_snapshot(print(export_table(out, table_width = 60, empty_line = "-", sep = " | ", remove_duplicates = FALSE)))
-  expect_snapshot(print(export_table(out, table_width = 60, empty_line = "-", cross = "+", remove_duplicates = FALSE)))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    empty_line = "-",
+    remove_duplicates = FALSE
+  )))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    empty_line = "-",
+    sep = " | ",
+    remove_duplicates = FALSE
+  )))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    empty_line = "-",
+    cross = "+",
+    remove_duplicates = FALSE
+  )))
   # don't remove duplicates
   expect_snapshot(print(export_table(out, table_width = 60, remove_duplicates = TRUE)))
-  expect_snapshot(print(export_table(out, table_width = 60, empty_line = "-", remove_duplicates = TRUE)))
-  expect_snapshot(print(export_table(out, table_width = 60, empty_line = "-", sep = " | ", remove_duplicates = TRUE)))
-  expect_snapshot(print(export_table(out, table_width = 60, empty_line = "-", cross = "+", remove_duplicates = TRUE)))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    empty_line = "-",
+    remove_duplicates = TRUE
+  )))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    empty_line = "-",
+    sep = " | ",
+    remove_duplicates = TRUE
+  )))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    empty_line = "-",
+    cross = "+",
+    remove_duplicates = TRUE
+  )))
 
   data(efc_insight, package = "insight")
   out <- datawizard::data_codebook(efc_insight[, 1:4])
   out$.row_id <- NULL
-  expect_snapshot(print(export_table(out, table_width = 60, remove_duplicates = TRUE, empty_line = "-", cross = "+")))
-  expect_snapshot(print(export_table(out, table_width = 60, remove_duplicates = FALSE, empty_line = "-", cross = "+")))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    remove_duplicates = TRUE,
+    empty_line = "-",
+    cross = "+"
+  )))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    remove_duplicates = FALSE,
+    empty_line = "-",
+    cross = "+"
+  )))
   out <- datawizard::data_codebook(efc_insight[, 1:3])
   out$.row_id <- NULL
-  expect_snapshot(print(export_table(out, table_width = 60, remove_duplicates = TRUE, empty_line = "-", cross = "+")))
-  expect_snapshot(print(export_table(out, table_width = 60, remove_duplicates = FALSE, empty_line = "-", cross = "+")))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    remove_duplicates = TRUE,
+    empty_line = "-",
+    cross = "+"
+  )))
+  expect_snapshot(print(export_table(
+    out,
+    table_width = 60,
+    remove_duplicates = FALSE,
+    empty_line = "-",
+    cross = "+"
+  )))
 })
 
 
@@ -202,7 +294,11 @@ test_that("export_table, overlengthy lines", {
 test_that("export_table, gt, simple", {
   skip_if_not_installed("gt")
   skip_on_cran()
-  d <- data.frame(a = c(1.3, 2, 543), b = c("ab", "cd", "abcde"), stringsAsFactors = FALSE)
+  d <- data.frame(
+    a = c(1.3, 2, 543),
+    b = c("ab", "cd", "abcde"),
+    stringsAsFactors = FALSE
+  )
   attr(d, "table_caption") <- "Table Title"
   set.seed(123)
   out <- gt::as_raw_html(export_table(d, format = "html"))
@@ -238,7 +334,8 @@ test_that("export_table, gt, complex with group indention", {
   cp <- parameters::compare_parameters(lm1, lm2, drop = "^\\(Intercept")
 
   set.seed(123)
-  out <- gt::as_raw_html(print_html(cp,
+  out <- gt::as_raw_html(print_html(
+    cp,
     select = "{estimate}{stars}|({se})",
     groups = list(
       Species = c(
@@ -260,12 +357,12 @@ test_that("export_table, new column names", {
   x <- as.data.frame(iris[1:5, ])
   out <- export_table(x, column_names = letters[1:5])
   expect_identical(
-    strsplit(out, "\n")[[1]][1],
+    strsplit(out, "\n", fixed = TRUE)[[1]][1],
     "   a |    b |    c |    d |      e"
   )
   out <- export_table(x, column_names = c(Species = "a"))
   expect_identical(
-    strsplit(out, "\n")[[1]][1],
+    strsplit(out, "\n", fixed = TRUE)[[1]][1],
     "Sepal.Length | Sepal.Width | Petal.Length | Petal.Width |      a"
   )
 
@@ -360,6 +457,7 @@ test_that("export_table, tinytable with indented rows", {
   expect_snapshot(export_table(mp, format = "tt", table_width = Inf))
 
   mp <- as.data.frame(format(parameters::model_parameters(model, drop = "^\\(Intercept")))
+  # fmt: skip
   mp$groups <- c(
     "Engine", "Controls", "Controls", "Engine", "Engine", "Engine", "Controls",
     "Interactions", "Interactions"
@@ -389,3 +487,30 @@ test_that("export_table, removing captions work", {
   out <- gt::as_raw_html(print_html(means, footer = "", caption = ""))
   expect_snapshot(as.character(out))
 })
+
+test_that("export_table with big_mark", {
+  # Test with comma separator
+  d <- data.frame(
+    x = c(1234.56, 9876543.21, 12.34),
+    y = c("a", "b", "c"),
+    stringsAsFactors = FALSE
+  )
+  out <- export_table(d, big_mark = ",", format = "text")
+  expect_true(any(grepl("1,234.56", out, fixed = TRUE)))
+  expect_true(any(grepl("9,876,543.21", out, fixed = TRUE)))
+
+  # Test with space separator
+  out <- export_table(d, big_mark = " ", format = "text")
+  expect_true(any(grepl("1 234.56", out, fixed = TRUE)))
+  expect_true(any(grepl("9 876 543.21", out, fixed = TRUE)))
+
+  # Test with markdown format
+  out <- export_table(d, big_mark = ",", format = "md")
+  expect_true(any(grepl("1,234.56", out, fixed = TRUE)))
+  expect_true(any(grepl("9,876,543.21", out, fixed = TRUE)))
+
+  # Test backward compatibility - no big_mark
+  out <- export_table(d, format = "text")
+  expect_true(any(grepl("1234.56", out, fixed = TRUE)))
+  expect_true(any(grepl("9.88e+06", out, fixed = TRUE)))
+})
diff --git a/tests/testthat/test-format.R b/tests/testthat/test-format.R
index ab6c6b717..4009d7f34 100644
--- a/tests/testthat/test-format.R
+++ b/tests/testthat/test-format.R
@@ -6,22 +6,45 @@ test_that("format_value", {
   expect_identical(format_value(0), "0.00")
   expect_identical(format_value(0, decimal_point = ","), "0,00")
   expect_identical(format_value(1234565789101112), "1.23e+15")
-  expect_identical(format_value(1234565789101112, protect_integers = TRUE), "1234565789101112")
+  expect_identical(
+    format_value(1234565789101112, protect_integers = TRUE),
+    "1234565789101112"
+  )
   expect_identical(format_value(0.0000000123), "1.23e-08")
   expect_identical(format_value(0.0000000123, zap_small = TRUE), "0.00")
   expect_identical(format_value(0.0000000123, digits = 8), "0.00000001")
-  expect_identical(format_value(c(0.012, 0.45, -0.03), lead_zero = FALSE), c(".01", ".45", "-.03"))
-  expect_identical(format_value(c(1.012, 0.45, -0.03), lead_zero = FALSE), c("1.01", ".45", "-.03"))
-  expect_identical(format_value(c(1.012, 0.45, -0.03), lead_zero = FALSE, decimal_point = ","), c("1,01", ",45", "-,03"))
-  expect_identical(format_value(c(0.45, -0.03), style_positive = "plus"), c("+0.45", "-0.03"))
-  expect_identical(format_value(c(0.45, -0.03), style_positive = "plus", lead_zero = FALSE), c("+.45", "-.03"))
+  expect_identical(
+    format_value(c(0.012, 0.45, -0.03), lead_zero = FALSE),
+    c(".01", ".45", "-.03")
+  )
+  expect_identical(
+    format_value(c(1.012, 0.45, -0.03), lead_zero = FALSE),
+    c("1.01", ".45", "-.03")
+  )
+  expect_identical(
+    format_value(c(1.012, 0.45, -0.03), lead_zero = FALSE, decimal_point = ","),
+    c("1,01", ",45", "-,03")
+  )
+  expect_identical(
+    format_value(c(0.45, -0.03), style_positive = "plus"),
+    c("+0.45", "-0.03")
+  )
+  expect_identical(
+    format_value(c(0.45, -0.03), style_positive = "plus", lead_zero = FALSE),
+    c("+.45", "-.03")
+  )
   expect_equal(
     format_value(as.factor(c("A", "B", "A"))),
     structure(c(1L, 2L, 1L), levels = c("A", "B"), class = "factor"),
     ignore_attr = TRUE
   )
   expect_identical(
-    format_value(c(0.45, -0.03), style_positive = "plus", style_negative = "parens", lead_zero = FALSE),
+    format_value(
+      c(0.45, -0.03),
+      style_positive = "plus",
+      style_negative = "parens",
+      lead_zero = FALSE
+    ),
     c("+.45", "(.03)")
   )
   expect_identical(
@@ -41,26 +64,107 @@ test_that("format_value", {
   expect_identical(format_value(0.00045, digits = 4), "0.0004")
 })
 
+test_that("format_value with big_mark", {
+  # Test basic thousands separator with comma
+  expect_identical(format_value(1234.56, big_mark = ","), "1,234.56")
+  expect_identical(format_value(1234567.89, big_mark = ","), "1,234,567.89")
+
+  # Test with space separator
+  expect_identical(format_value(1234.56, big_mark = " "), "1 234.56")
+  expect_identical(format_value(1234567.89, big_mark = " "), "1 234 567.89")
+
+  # Test with protect_integers
+  expect_identical(format_value(1234, big_mark = ",", protect_integers = TRUE), "1,234")
+  expect_identical(format_value(1234.0, big_mark = ",", protect_integers = TRUE), "1,234")
+
+  # Test with vectors
+  expect_identical(
+    format_value(c(1234.56, 987654.32, 12.34), big_mark = ","),
+    c("1,234.56", "987,654.32", "12.34")
+  )
+
+  # Test with negative numbers
+  expect_identical(format_value(-1234.56, big_mark = ","), "-1,234.56")
+  expect_identical(format_value(-1234567.89, big_mark = ","), "-1,234,567.89")
+
+  # Test that NULL or empty string disables thousands separator (backward compatibility)
+  expect_identical(format_value(1234.56, big_mark = NULL), "1234.56")
+  expect_identical(format_value(1234.56, big_mark = ""), "1234.56")
+
+  # Test very large numbers - when big_mark is provided, scientific notation is suppressed
+  # to show the full number with separators
+  expect_identical(
+    format_value(1234565789101112, big_mark = ","),
+    "1,234,565,789,101,112.00"
+  )
+
+  # Test that without big_mark, very large numbers still use scientific notation
+  expect_identical(format_value(1234565789101112), "1.23e+15")
+
+  # Test with decimal_point and big_mark together
+  expect_identical(format_value(1234.56, big_mark = ",", decimal_point = ","), "1,234,56")
+  expect_identical(format_value(1234.56, big_mark = " ", decimal_point = ","), "1 234,56")
+
+  # Test that percentages are not affected by big_mark (they have % sign)
+  # Percentages don't typically need thousands separators in their display
+  expect_identical(format_value(0.95, as_percent = TRUE, big_mark = ","), "95.00%")
+  expect_identical(format_value(12.345, as_percent = TRUE, big_mark = ","), "1,234.50%")
+})
+
+test_that("format_number with big_mark", {
+  # Test that format_number passes big_mark when textual=FALSE
+  expect_identical(format_number(1234.56, textual = FALSE, big_mark = ","), "1,234.56")
+  expect_identical(
+    format_number(1234567.89, textual = FALSE, big_mark = " "),
+    "1 234 567.89"
+  )
+})
+
 test_that("format_ci", {
   expect_identical(
     format_ci(c(123, 123, 123, 123), c(123, 12345, 123456, 123456789012), width = "auto"),
-    c("95% CI [123.00,   123.00]", "95% CI [123.00, 12345.00]", "95% CI [123.00, 1.23e+05]", "95% CI [123.00, 1.23e+11]")
+    c(
+      "95% CI [123.00,   123.00]",
+      "95% CI [123.00, 12345.00]",
+      "95% CI [123.00, 1.23e+05]",
+      "95% CI [123.00, 1.23e+11]"
+    )
   )
   expect_identical(
-    format_ci(c(123, 123, 123, 123), c(123, 12345, 123456, 123456789012), width = "auto", digits = 5),
+    format_ci(
+      c(123, 123, 123, 123),
+      c(123, 12345, 123456, 123456789012),
+      width = "auto",
+      digits = 5
+    ),
     c(
-      "95% CI [123.00000,   123.00000]", "95% CI [123.00000, 12345.00000]",
-      "95% CI [123.00000, 1.23456e+05]", "95% CI [123.00000, 1.23457e+11]"
+      "95% CI [123.00000,   123.00000]",
+      "95% CI [123.00000, 12345.00000]",
+      "95% CI [123.00000, 1.23456e+05]",
+      "95% CI [123.00000, 1.23457e+11]"
     )
   )
   expect_identical(
-    format_ci(c(123, 123, 123, 123), c(123, 12345, 123456, 123456789012), width = "auto", digits = 0),
-    c("95% CI [123,    123]", "95% CI [123,  12345]", "95% CI [123,  1e+05]", "95% CI [123,  1e+11]")
+    format_ci(
+      c(123, 123, 123, 123),
+      c(123, 12345, 123456, 123456789012),
+      width = "auto",
+      digits = 0
+    ),
+    c(
+      "95% CI [123,    123]",
+      "95% CI [123,  12345]",
+      "95% CI [123,  1e+05]",
+      "95% CI [123,  1e+11]"
+    )
   )
   expect_identical(format_ci(1.24, 0.0000054), "95% CI [1.24, 5.40e-06]")
   expect_identical(format_ci(1.24, 0.0000054, digits = 0), "95% CI [1, 5e-06]")
   expect_identical(format_ci(1.24, 0.0000054, zap_small = TRUE), "95% CI [1.24, 0.00]")
-  expect_identical(format_ci(1.24, 0.0000054, zap_small = TRUE, digits = 0), "95% CI [1, 0]")
+  expect_identical(
+    format_ci(1.24, 0.0000054, zap_small = TRUE, digits = 0),
+    "95% CI [1, 0]"
+  )
 })
 
 test_that("format_ci, bayestestR", {
@@ -78,7 +182,9 @@ test_that("format_ci, parameters", {
   expect_identical(
     format_ci(parameters::ci(mm)),
     c(
-      "95% CI [4.62, 4.94]", "95% CI [0.53, 1.30]", "95% CI [-0.52, 0.40]",
+      "95% CI [4.62, 4.94]",
+      "95% CI [0.53, 1.30]",
+      "95% CI [-0.52, 0.40]",
       "95% CI [-0.76, 0.66]"
     )
   )
@@ -178,7 +284,13 @@ test_that("format_table, other CI columns", {
   attr(x, "ci") <- 0.8
   attr(x, "ci_test") <- 0.9
   test <- utils::capture.output(format_table(x))
-  expect_identical(test, c("        80% CI  test 80% CI other 80% CI", "1 [2.43, 5.45] [0.10, 1.30] [0.12, 1.40]"))
+  expect_identical(
+    test,
+    c(
+      "        80% CI  test 80% CI other 80% CI",
+      "1 [2.43, 5.45] [0.10, 1.30] [0.12, 1.40]"
+    )
+  )
 })
 
 
@@ -210,7 +322,6 @@ test_that("format_table, multiple CI columns", {
     ignore_attr = TRUE
   )
 
-
   # d <- data.frame(
   #   Parameter = c("(Intercept)", "wt", "cyl"),
   #   Coefficient = c(39.69, -3.19, -1.51),
@@ -244,6 +355,9 @@ test_that("format_table, preserve attributes", {
   attr(d, "table_footer") <- "This is a footer"
   attr(d, "table_caption") <- "And the caption"
   d2 <- insight::format_table(d, digits = 3, preserve_attributes = TRUE)
-  expect_named(attributes(d2), c("names", "row.names", "class", "table_footer", "table_caption"))
+  expect_named(
+    attributes(d2),
+    c("names", "row.names", "class", "table_footer", "table_caption")
+  )
   expect_identical(attributes(d2)$table_caption, "And the caption")
 })
diff --git a/tests/testthat/test-lcmm.R b/tests/testthat/test-lcmm.R
index fbc85b1e2..28ac5bc75 100644
--- a/tests/testthat/test-lcmm.R
+++ b/tests/testthat/test-lcmm.R
@@ -68,7 +68,7 @@ test_that("find_formula", {
 
   expect_equal(
     find_formula(m3),
-    list(classmb = ~X1 + X2 + X3),
+    list(classmb = ~ X1 + X2 + X3),
     ignore_attr = TRUE
   )
 })