diff --git a/src/app/commands/cmd_new_sprite_from_selection.cpp b/src/app/commands/cmd_new_sprite_from_selection.cpp
index e14dd87fe..65e654277 100644
--- a/src/app/commands/cmd_new_sprite_from_selection.cpp
+++ b/src/app/commands/cmd_new_sprite_from_selection.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2019  Igara Studio S.A.
+// Copyright (C) 2018-2023  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -21,6 +21,7 @@
 #include "doc/mask.h"
 #include "doc/palette.h"
 #include "doc/sprite.h"
+#include "fmt/format.h"
 
 #include <cstdio>
 
@@ -80,11 +81,13 @@ void NewSpriteFromSelectionCommand::onExecute(Context* context)
 
   std::unique_ptr<Doc> dstDoc(new Doc(dstSprite.get()));
   dstSprite.release();
-  char buf[1024];
-  std::sprintf(buf, "%s-%dx%d-%dx%d",
-               base::get_file_title(doc->filename()).c_str(),
-               mask->bounds().x, mask->bounds().y,
-               mask->bounds().w, mask->bounds().h);
+
+  const std::string buf =
+    fmt::format("{}-{}x{}-{}x{}",
+                base::get_file_title(doc->filename()),
+                mask->bounds().x, mask->bounds().y,
+                mask->bounds().w, mask->bounds().h);
+
   dstDoc->setFilename(buf);
   dstDoc->setContext(context);
   dstDoc.release();
diff --git a/src/app/commands/filters/filter_target_buttons.cpp b/src/app/commands/filters/filter_target_buttons.cpp
index 1082c3004..82a3a8089 100644
--- a/src/app/commands/filters/filter_target_buttons.cpp
+++ b/src/app/commands/filters/filter_target_buttons.cpp
@@ -16,6 +16,7 @@
 #include "app/modules/gui.h"
 #include "app/ui/skin/skin_theme.h"
 #include "doc/image.h"
+#include "fmt/format.h"
 #include "ui/box.h"
 #include "ui/button.h"
 #include "ui/theme.h"
@@ -115,10 +116,10 @@ void FilterTargetButtons::updateFromCelsTarget()
 void FilterTargetButtons::updateComponentTooltip(Item* item, const char* channelName, int align)
 {
   if (item) {
-    char buf[256];
-    std::sprintf(buf, "%s %s Component",
-                 (item->isSelected() ? "Modify": "Ignore"),
-                 channelName);
+    std::string buf =
+      fmt::format("{} {} Component",
+                  (item->isSelected() ? "Modify": "Ignore"),
+                  channelName);
     m_tooltips.addTooltipFor(item, buf, align);
   }
 }
diff --git a/src/app/crash/data_recovery.cpp b/src/app/crash/data_recovery.cpp
index 9ac528975..b9348930c 100644
--- a/src/app/crash/data_recovery.cpp
+++ b/src/app/crash/data_recovery.cpp
@@ -19,6 +19,7 @@
 #include "base/fs.h"
 #include "base/thread.h"
 #include "base/time.h"
+#include "fmt/format.h"
 #include "ui/system.h"
 
 #include <algorithm>
@@ -55,10 +56,10 @@ DataRecovery::DataRecovery(Context* ctx)
   do {
     base::Time time = base::current_time();
 
-    char buf[1024];
-    sprintf(buf, "%04d%02d%02d-%02d%02d%02d-%d",
-      time.year, time.month, time.day,
-      time.hour, time.minute, time.second, pid);
+    std::string buf =
+      fmt::format("{:04}{:02}{:02}-{:02}{:02}{:02}-{}",
+                  time.year, time.month, time.day,
+                  time.hour, time.minute, time.second, pid);
 
     newSessionDir = base::join_path(m_sessionsDir, buf);
 
diff --git a/src/app/file/file.cpp b/src/app/file/file.cpp
index 95f592788..830beb2c6 100644
--- a/src/app/file/file.cpp
+++ b/src/app/file/file.cpp
@@ -401,7 +401,7 @@ FileOp* FileOp::createLoadDocumentOperation(Context* context,
     if (!(flags & FILE_LOAD_SEQUENCE_NONE)) {
       std::string left, right;
       int c, width, start_from;
-      char buf[512];
+      std::string buf;
 
       // First of all, we must generate the list of files to load in the
       // sequence...
@@ -412,7 +412,7 @@ FileOp* FileOp::createLoadDocumentOperation(Context* context,
         // Try to get more file names
         for (c=start_from+1; ; c++) {
           // Get the next file name
-          sprintf(buf, "%s%0*d%s", left.c_str(), width, c, right.c_str());
+          buf = fmt::format("{0}{1:0{2}d}{3}", left, c, width, right);
 
           // If the file doesn't exist, we doesn't need more files to load
           if (!base::is_file(buf))
diff --git a/src/app/file/file_data.cpp b/src/app/file/file_data.cpp
index 9645b9d87..6d3acc7a4 100644
--- a/src/app/file/file_data.cpp
+++ b/src/app/file/file_data.cpp
@@ -18,6 +18,7 @@
 #include "doc/color.h"
 #include "doc/document.h"
 #include "doc/slice.h"
+#include "fmt/format.h"
 #include "gfx/color.h"
 
 #include <cstdlib>
@@ -33,19 +34,19 @@ namespace {
 
 std::string color_to_hex(doc::color_t color)
 {
-  char buf[256];
+  std::string buf;
   if (doc::rgba_geta(color) == 255) {
-    std::sprintf(buf, "#%02x%02x%02x",
-                 doc::rgba_getr(color),
-                 doc::rgba_getg(color),
-                 doc::rgba_getb(color));
+    buf = fmt::format("#{:02x}{:02x}{:02x}",
+                      doc::rgba_getr(color),
+                      doc::rgba_getg(color),
+                      doc::rgba_getb(color));
   }
   else {
-    std::sprintf(buf, "#%02x%02x%02x%02x",
-                 doc::rgba_getr(color),
-                 doc::rgba_getg(color),
-                 doc::rgba_getb(color),
-                 doc::rgba_geta(color));
+    buf = fmt::format("#{:02x}{:02x}{:02x}{:02x}",
+                      doc::rgba_getr(color),
+                      doc::rgba_getg(color),
+                      doc::rgba_getb(color),
+                      doc::rgba_geta(color));
   }
   return buf;
 }
diff --git a/src/app/file/file_tests.cpp b/src/app/file/file_tests.cpp
index f888f99ff..0963cd4c4 100644
--- a/src/app/file/file_tests.cpp
+++ b/src/app/file/file_tests.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2019  Igara Studio S.A.
+// Copyright (C) 2018-2023  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -15,6 +15,7 @@
 #include "base/base64.h"
 #include "doc/doc.h"
 #include "doc/user_data.h"
+#include "fmt/format.h"
 
 #include <cstdio>
 #include <cstdlib>
@@ -27,18 +28,18 @@ using namespace app;
 TEST(File, SeveralSizes)
 {
   // Register all possible image formats.
-  std::vector<char> fn(256);
+  std::string fn;
   app::Context ctx;
 
   for (int w=10; w<=10+503*2; w+=503) {
     for (int h=10; h<=10+503*2; h+=503) {
-      //std::sprintf(&fn[0], "test_%dx%d.ase", w, h);
-      std::sprintf(&fn[0], "test.ase");
+      //fn = fmt::format("test_{}x{}.ase", w, h);
+      fn = "test.ase";
 
       {
         std::unique_ptr<Doc> doc(
           ctx.documents().add(w, h, doc::ColorMode::INDEXED, 256));
-        doc->setFilename(&fn[0]);
+        doc->setFilename(fn);
 
         // Random pixels
         Layer* layer = doc->sprite()->root()->firstLayer();
@@ -59,7 +60,7 @@ TEST(File, SeveralSizes)
       }
 
       {
-        std::unique_ptr<Doc> doc(load_document(&ctx, &fn[0]));
+        std::unique_ptr<Doc> doc(load_document(&ctx, fn));
         ASSERT_EQ(w, doc->sprite()->width());
         ASSERT_EQ(h, doc->sprite()->height());
 
diff --git a/src/app/filename_formatter.cpp b/src/app/filename_formatter.cpp
index a17a77bdc..cb0f7fff9 100644
--- a/src/app/filename_formatter.cpp
+++ b/src/app/filename_formatter.cpp
@@ -16,6 +16,7 @@
 #include "base/convert_to.h"
 #include "base/fs.h"
 #include "base/replace_string.h"
+#include "fmt/format.h"
 
 #include <cstdlib>
 #include <cstring>
@@ -35,14 +36,17 @@ static bool replace_frame(const char* frameKey, // E.g. = "{frame"
     if (j != std::string::npos) {
       std::string from = str.substr(i, j - i + 1);
       if (frameBase >= 0) {
-        std::vector<char> to(32);
         int offset = std::strtol(from.c_str()+keyLen, NULL, 10);
 
-        std::sprintf(&to[0], "%0*d", (int(j)-int(i+keyLen)), frameBase + offset);
-        base::replace_string(str, from, &to[0]);
+        const std::string to =
+          fmt::format("{0:0{1}d}",
+                      frameBase + offset,
+                      (int(j)-int(i+keyLen)));
+
+        base::replace_string(str, from, to);
       }
       else
-        base::replace_string(str, from, "");
+        base::replace_string(str, from, std::string());
     }
     return true;
   }
@@ -59,9 +63,7 @@ static bool autodetect_frame_format(const std::string& filename,
   int frameWidth = 0;
   frameBase = split_filename(filename, left, right, frameWidth);
   if (frameBase >= 0) {
-    std::vector<char> buf(32);
-    std::sprintf(&buf[0], "{frame%0*d}", frameWidth, frameBase);
-    frameFormat = std::string(&buf[0]);
+    frameFormat = fmt::format("{{frame{0:0{1}d}}}", frameBase, frameWidth);
     return true;
   }
   else
diff --git a/src/app/ini_file.cpp b/src/app/ini_file.cpp
index c6022b57e..ddb3f8442 100644
--- a/src/app/ini_file.cpp
+++ b/src/app/ini_file.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2018-2021  Igara Studio S.A.
+// Copyright (C) 2018-2023  Igara Studio S.A.
 // Copyright (C) 2001-2016  David Capello
 //
 // This program is distributed under the terms of
@@ -16,6 +16,7 @@
 #include "base/split_string.h"
 #include "base/string.h"
 #include "cfg/cfg.h"
+#include "fmt/format.h"
 
 #ifdef __APPLE__
 #include "os/logger.h"
@@ -208,9 +209,8 @@ Point get_config_point(const char* section, const char* name, const Point& point
 
 void set_config_point(const char* section, const char* name, const Point& point)
 {
-  char buf[128];
-  sprintf(buf, "%d %d", point.x, point.y);
-  set_config_string(section, name, buf);
+  std::string buf = fmt::format("{} {}", point.x, point.y);
+  set_config_string(section, name, buf.c_str());
 }
 
 Size get_config_size(const char* section, const char* name, const Size& size)
@@ -230,9 +230,8 @@ Size get_config_size(const char* section, const char* name, const Size& size)
 
 void set_config_size(const char* section, const char* name, const Size& size)
 {
-  char buf[128];
-  sprintf(buf, "%d %d", size.w, size.h);
-  set_config_string(section, name, buf);
+  std::string buf = fmt::format("{} {}", size.w, size.h);
+  set_config_string(section, name, buf.c_str());
 }
 
 Rect get_config_rect(const char* section, const char* name, const Rect& rect)
@@ -254,9 +253,8 @@ Rect get_config_rect(const char* section, const char* name, const Rect& rect)
 
 void set_config_rect(const char* section, const char* name, const Rect& rect)
 {
-  char buf[128];
-  sprintf(buf, "%d %d %d %d", rect.x, rect.y, rect.w, rect.h);
-  set_config_string(section, name, buf);
+  std::string buf = fmt::format("{} {} {} {}", rect.x, rect.y, rect.w, rect.h);
+  set_config_string(section, name, buf.c_str());
 }
 
 app::Color get_config_color(const char* section, const char* name, const app::Color& value)
diff --git a/src/app/resource_finder.cpp b/src/app/resource_finder.cpp
index ef056bf5d..3a3126c6c 100644
--- a/src/app/resource_finder.cpp
+++ b/src/app/resource_finder.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2019-2021  Igara Studio S.A.
+// Copyright (C) 2019-2023  Igara Studio S.A.
 // Copyright (C) 2001-2016  David Capello
 //
 // This program is distributed under the terms of
@@ -89,31 +89,31 @@ void ResourceFinder::includeDataDir(const char* filename)
 
 #ifdef _WIN32
 
-  sprintf(buf, "data/%s", filename);
+  std::snprintf(buf, sizeof(buf), "data/%s", filename);
   includeHomeDir(buf); // %AppData%/Aseprite/data/filename
   includeBinDir(buf);  // $BINDIR/data/filename
 
 #elif __APPLE__
 
-  sprintf(buf, "data/%s", filename);
+  std::snprintf(buf, sizeof(buf), "data/%s", filename);
   includeUserDir(buf); // $HOME/Library/Application Support/Aseprite/data/filename
   includeBinDir(buf);  // $BINDIR/data/filename (outside the bundle)
 
-  sprintf(buf, "../Resources/data/%s", filename);
+  std::snprintf(buf, sizeof(buf), "../Resources/data/%s", filename);
   includeBinDir(buf);  // $BINDIR/../Resources/data/filename (inside a bundle)
 
 #else
 
   // $HOME/.config/aseprite/filename
-  sprintf(buf, "aseprite/data/%s", filename);
+  std::snprintf(buf, sizeof(buf), "aseprite/data/%s", filename);
   includeHomeConfigDir(buf);
 
   // $BINDIR/data/filename
-  sprintf(buf, "data/%s", filename);
+  std::snprintf(buf, sizeof(buf), "data/%s", filename);
   includeBinDir(buf);
 
   // $BINDIR/../share/aseprite/data/filename (installed in /usr/ or /usr/local/)
-  sprintf(buf, "../share/aseprite/data/%s", filename);
+  std::snprintf(buf, sizeof(buf), "../share/aseprite/data/%s", filename);
   includeBinDir(buf);
 
 #endif
@@ -139,7 +139,7 @@ void ResourceFinder::includeHomeDir(const char* filename)
 
   if ((env) && (*env)) {
     // $HOME/filename
-    sprintf(buf, "%s/%s", env, filename);
+    std::snprintf(buf, sizeof(buf), "%s/%s", env, filename);
     addPath(buf);
   }
   else {
diff --git a/src/app/shade.cpp b/src/app/shade.cpp
index 36a494e6f..b08840fa8 100644
--- a/src/app/shade.cpp
+++ b/src/app/shade.cpp
@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2023  Igara Studio S.A.
 // Copyright (C) 2001-2015  David Capello
 //
 // This program is distributed under the terms of
@@ -31,8 +32,9 @@ std::string shade_to_string(const Shade& shade)
 {
   std::string res;
   for (const auto& s : shade) {
+    if (!res.empty())
+      res += " ";
     res += s.toString();
-    res += " ";
   }
   return res;
 }
diff --git a/src/app/tools/controllers.h b/src/app/tools/controllers.h
index 048f62d6a..73ab52ccb 100644
--- a/src/app/tools/controllers.h
+++ b/src/app/tools/controllers.h
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2019-2022  Igara Studio S.A.
+// Copyright (C) 2019-2023  Igara Studio S.A.
 // Copyright (C) 2001-2018  David Capello
 //
 // This program is distributed under the terms of
@@ -8,6 +8,7 @@
 #include "app/snap_to_grid.h"
 #include "base/gcd.h"
 #include "base/pi.h"
+#include "fmt/format.h"
 
 #include <algorithm>
 #include <cmath>
@@ -93,13 +94,12 @@ public:
       return;
 
     gfx::Point offset = loop->statusBarPositionOffset();
-    char buf[1024];
-    sprintf(buf, ":start: %d %d :end: %d %d",
-            stroke.firstPoint().x+offset.x,
-            stroke.firstPoint().y+offset.y,
-            stroke.lastPoint().x+offset.x,
-            stroke.lastPoint().y+offset.y);
-    text = buf;
+    text = fmt::format(
+      ":start: {} {} :end: {} {}",
+      stroke.firstPoint().x+offset.x,
+      stroke.firstPoint().y+offset.y,
+      stroke.lastPoint().x+offset.x,
+      stroke.lastPoint().y+offset.y);
   }
 
 private:
@@ -253,16 +253,16 @@ public:
     if (stroke.size() < 2)
       return;
 
-    int w = ABS(stroke[1].x-stroke[0].x)+1;
-    int h = ABS(stroke[1].y-stroke[0].y)+1;
+    const int w = ABS(stroke[1].x-stroke[0].x)+1;
+    const int h = ABS(stroke[1].y-stroke[0].y)+1;
 
-    gfx::Point offset = loop->statusBarPositionOffset();
-    char buf[1024];
-    int gcd = base::gcd(w, h);
-    sprintf(buf, ":start: %d %d :end: %d %d :size: %d %d :distance: %.1f",
-            stroke[0].x+offset.x, stroke[0].y+offset.y,
-            stroke[1].x+offset.x, stroke[1].y+offset.y,
-            w, h, std::sqrt(w*w + h*h));
+    const gfx::Point offset = loop->statusBarPositionOffset();
+    const int gcd = base::gcd(w, h);
+
+    text = fmt::format(":start: {} {} :end: {} {} :size: {} {} :distance: {:.1f}",
+                       stroke[0].x+offset.x, stroke[0].y+offset.y,
+                       stroke[1].x+offset.x, stroke[1].y+offset.y,
+                       w, h, std::sqrt(w*w + h*h));
 
     if (hasAngle() ||
         loop->getIntertwine()->snapByAngle()) {
@@ -272,14 +272,12 @@ public:
       else
         angle = std::atan2(static_cast<double>(stroke[0].y-stroke[1].y),
                            static_cast<double>(stroke[1].x-stroke[0].x));
-      sprintf(buf+strlen(buf), " :angle: %.1f", 180.0 * angle / PI);
+      text += fmt::format(" :angle: {:.1f}", 180.0 * angle / PI);
     }
 
     // Aspect ratio at the end
-    sprintf(buf+strlen(buf), " :aspect_ratio: %d:%d",
-            w/gcd, h/gcd);
-
-    text = buf;
+    text += fmt::format(" :aspect_ratio: {}:{}",
+                        w/gcd, h/gcd);
   }
 
   double getShapeAngle() const override {
@@ -361,13 +359,11 @@ public:
       return;
 
     gfx::Point offset = loop->statusBarPositionOffset();
-    char buf[1024];
-    sprintf(buf, ":start: %d %d :end: %d %d",
-            stroke.firstPoint().x+offset.x,
-            stroke.firstPoint().y+offset.y,
-            stroke.lastPoint().x+offset.x,
-            stroke.lastPoint().y+offset.y);
-    text = buf;
+    text = fmt::format(":start: {} {} :end: {} {}",
+                       stroke.firstPoint().x+offset.x,
+                       stroke.firstPoint().y+offset.y,
+                       stroke.lastPoint().x+offset.x,
+                       stroke.lastPoint().y+offset.y);
   }
 
 };
@@ -401,11 +397,9 @@ public:
       return;
 
     gfx::Point offset = loop->statusBarPositionOffset();
-    char buf[1024];
-    sprintf(buf, ":pos: %d %d",
-            stroke[0].x+offset.x,
-            stroke[0].y+offset.y);
-    text = buf;
+    text = fmt::format(":pos: {} {}",
+                       stroke[0].x+offset.x,
+                       stroke[0].y+offset.y);
   }
 
 };
@@ -459,14 +453,12 @@ public:
       return;
 
     gfx::Point offset = loop->statusBarPositionOffset();
-    char buf[1024];
-    sprintf(buf, ":start: %d %d :end: %d %d (%d %d - %d %d)",
-            stroke[0].x+offset.x, stroke[0].y+offset.y,
-            stroke[3].x+offset.x, stroke[3].y+offset.y,
-            stroke[1].x+offset.x, stroke[1].y+offset.y,
-            stroke[2].x+offset.x, stroke[2].y+offset.y);
 
-    text = buf;
+    text = fmt::format(":start: {} {} :end: {} {} ({} {} - {} {})",
+                       stroke[0].x+offset.x, stroke[0].y+offset.y,
+                       stroke[3].x+offset.x, stroke[3].y+offset.y,
+                       stroke[1].x+offset.x, stroke[1].y+offset.y,
+                       stroke[2].x+offset.x, stroke[2].y+offset.y);
   }
 
 private:
diff --git a/src/app/ui/context_bar.cpp b/src/app/ui/context_bar.cpp
index 1b22d4d0f..5afeccf2f 100644
--- a/src/app/ui/context_bar.cpp
+++ b/src/app/ui/context_bar.cpp
@@ -654,12 +654,13 @@ private:
 
     m_loaded = true;
 
-    char buf[32];
+    std::string buf;
     int n = get_config_int("shades", "count", 0);
     n = std::clamp(n, 0, 256);
     for (int i=0; i<n; ++i) {
-      sprintf(buf, "shade%d", i);
-      Shade shade = shade_from_string(get_config_string("shades", buf, ""));
+      buf = fmt::format("shade{}", i);
+      Shade shade = shade_from_string(
+        get_config_string("shades", buf.c_str(), ""));
       if (shade.size() >= 2)
         m_shades.push_back(shade);
     }
@@ -669,12 +670,13 @@ private:
     if (!m_loaded)
       return;
 
-    char buf[32];
+    std::string buf;
     int n = int(m_shades.size());
     set_config_int("shades", "count", n);
     for (int i=0; i<n; ++i) {
-      sprintf(buf, "shade%d", i);
-      set_config_string("shades", buf, shade_to_string(m_shades[i]).c_str());
+      buf = fmt::format("shade{}", i);
+      set_config_string("shades", buf.c_str(),
+                        shade_to_string(m_shades[i]).c_str());
     }
   }
 
diff --git a/src/app/ui/editor/editor.cpp b/src/app/ui/editor/editor.cpp
index f6df2a7b0..2cbf49b44 100644
--- a/src/app/ui/editor/editor.cpp
+++ b/src/app/ui/editor/editor.cpp
@@ -2243,10 +2243,10 @@ void Editor::onPaint(ui::PaintEvent& ev)
       if (Preferences::instance().perf.showRenderTime()) {
         View* view = View::getView(this);
         gfx::Rect vp = view->viewportBounds();
-        char buf[128];
-        sprintf(buf, "%c %.4gs",
-                Preferences::instance().experimental.newRenderEngine() ? 'N': 'O',
-                renderElapsed);
+        std::string buf =
+          fmt::format("{:c} {:.4g}s",
+                      Preferences::instance().experimental.newRenderEngine() ? 'N': 'O',
+                      renderElapsed);
         g->drawText(
           buf,
           gfx::rgba(255, 255, 255, 255),
diff --git a/src/app/ui/timeline/timeline.cpp b/src/app/ui/timeline/timeline.cpp
index 28b27045e..131dd7459 100644
--- a/src/app/ui/timeline/timeline.cpp
+++ b/src/app/ui/timeline/timeline.cpp
@@ -3746,7 +3746,7 @@ void Timeline::updateStatusBarForFrame(const frame_t frame,
   if (!m_sprite)
     return;
 
-  char buf[256] = { 0 };
+  std::string buf;
   frame_t base = docPref().timeline.firstFrame();
   frame_t firstFrame = frame;
   frame_t lastFrame = frame;
@@ -3761,41 +3761,34 @@ void Timeline::updateStatusBarForFrame(const frame_t frame,
     lastFrame = m_range.lastFrame();
   }
 
-  std::sprintf(
-    buf+std::strlen(buf), ":frame: %d",
-    base+frame);
+  buf += fmt::format(":frame: {}",
+                     int(base+frame));
   if (firstFrame != lastFrame) {
-    std::sprintf(
-      buf+std::strlen(buf), " [%d...%d]",
-      int(base+firstFrame),
-      int(base+lastFrame));
+    buf += fmt::format(" [{}...{}]",
+                       int(base+firstFrame),
+                       int(base+lastFrame));
   }
 
-  std::sprintf(
-    buf+std::strlen(buf), " :clock: %s",
-    human_readable_time(m_sprite->frameDuration(frame)).c_str());
+  buf += fmt::format(" :clock: {}",
+                     human_readable_time(m_sprite->frameDuration(frame)));
   if (firstFrame != lastFrame) {
-    std::sprintf(
-      buf+std::strlen(buf), " [%s]",
-      tag ?
-      human_readable_time(tagFramesDuration(tag)).c_str():
-      human_readable_time(selectedFramesDuration()).c_str());
+    buf += fmt::format(" [{}]",
+                       tag ?
+                       human_readable_time(tagFramesDuration(tag)):
+                       human_readable_time(selectedFramesDuration()));
   }
   if (m_sprite->totalFrames() > 1)
-    std::sprintf(
-      buf+std::strlen(buf), "/%s",
-      human_readable_time(m_sprite->totalAnimationDuration()).c_str());
+    buf += fmt::format("/{}",
+                       human_readable_time(m_sprite->totalAnimationDuration()));
 
   if (cel) {
-    std::sprintf(
-      buf+std::strlen(buf), " Cel :pos: %d %d :size: %d %d",
-      cel->bounds().x, cel->bounds().y,
-      cel->bounds().w, cel->bounds().h);
+    buf += fmt::format(" Cel :pos: {} {} :size: {} {}",
+                       cel->bounds().x, cel->bounds().y,
+                       cel->bounds().w, cel->bounds().h);
 
     if (cel->links() > 0) {
-      std::sprintf(
-        buf+std::strlen(buf), " Links %d",
-        int(cel->links()));
+      buf += fmt::format(" Links {}",
+                         int(cel->links()));
     }
   }
 
diff --git a/src/app/ui/zoom_entry.cpp b/src/app/ui/zoom_entry.cpp
index 916ad8875..e3fe2b12b 100644
--- a/src/app/ui/zoom_entry.cpp
+++ b/src/app/ui/zoom_entry.cpp
@@ -1,5 +1,5 @@
 // Aseprite
-// Copyright (C) 2021  Igara Studio S.A.
+// Copyright (C) 2021-2023  Igara Studio S.A.
 // Copyright (C) 2001-2017  David Capello
 //
 // This program is distributed under the terms of
@@ -13,6 +13,7 @@
 
 #include "app/modules/gui.h"
 #include "base/scoped_value.h"
+#include "fmt/format.h"
 #include "gfx/rect.h"
 #include "gfx/region.h"
 #include "ui/manager.h"
@@ -65,10 +66,7 @@ void ZoomEntry::onValueChange()
 std::string ZoomEntry::onGetTextFromValue(int value)
 {
   render::Zoom zoom = render::Zoom::fromLinearScale(value);
-
-  char buf[256];
-  std::sprintf(buf, "%.1f", zoom.scale() * 100.0);
-  return buf;
+  return fmt::format("{:.1f}", zoom.scale() * 100.0);
 }
 
 int ZoomEntry::onGetValueFromText(const std::string& text)
diff --git a/src/app/util/readable_time.cpp b/src/app/util/readable_time.cpp
index 363613c54..db487199e 100644
--- a/src/app/util/readable_time.cpp
+++ b/src/app/util/readable_time.cpp
@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2023  Igara Studio S.A.
 // Copyright (C) 2017  David Capello
 //
 // This program is distributed under the terms of
@@ -10,22 +11,20 @@
 
 #include "app/util/readable_time.h"
 
-#include <cstdio>
+#include "fmt/format.h"
 
 namespace app {
 
 std::string human_readable_time(const int t)
 {
-  char buf[32];
   if (t < 900)
-    std::sprintf(buf, "%dms", t);
+    return fmt::format("{:d}ms", t);
   else if (t < 1000*59)
-    std::sprintf(buf, "%0.2fs", double(t) / 1000.0);
+    return fmt::format("{:0.2f}s", double(t) / 1000.0);
   else if (t < 1000*60*59)
-    std::sprintf(buf, "%0.2fm", double(t) / 1000.0 / 60.0);
+    return fmt::format("{:0.2f}m", double(t) / 1000.0 / 60.0);
   else
-    std::sprintf(buf, "%0.2fh", double(t) / 1000.0 / 60.0 / 60.0);
-  return buf;
+    return fmt::format("{:0.2f}h", double(t) / 1000.0 / 60.0 / 60.0);
 }
 
 } // namespace app
diff --git a/src/app/xml_exception.cpp b/src/app/xml_exception.cpp
index 21dec2269..9aee17ed4 100644
--- a/src/app/xml_exception.cpp
+++ b/src/app/xml_exception.cpp
@@ -1,4 +1,5 @@
 // Aseprite
+// Copyright (C) 2023  Igara Studio S.A.
 // Copyright (C) 2001-2015  David Capello
 //
 // This program is distributed under the terms of
@@ -10,22 +11,18 @@
 
 #include "app/xml_exception.h"
 
+#include "fmt/format.h"
 #include "tinyxml.h"
 
-#include <cstdio>
-
 namespace app {
 
 XmlException::XmlException(const TiXmlDocument* doc) throw()
 {
   try {
-    char buf[4096];             // TODO Overflow
-
-    sprintf(buf, "Error in XML file '%s' (line %d, column %d)\nError %d: %s",
-            doc->Value(), doc->ErrorRow(), doc->ErrorCol(),
-            doc->ErrorId(), doc->ErrorDesc());
-
-    setMessage(buf);
+    setMessage(
+      fmt::format("Error in XML file '{}' (line {}, column {})\nError {}: {}",
+                  doc->Value(), doc->ErrorRow(), doc->ErrorCol(),
+                  doc->ErrorId(), doc->ErrorDesc()).c_str());
   }
   catch (...) {
     // No throw
diff --git a/src/ui/alert.cpp b/src/ui/alert.cpp
index 6bab0e458..0c611649c 100644
--- a/src/ui/alert.cpp
+++ b/src/ui/alert.cpp
@@ -121,7 +121,7 @@ void Alert::addButton(const std::string& text)
   m_buttons.push_back(button);
 
   char id[256];
-  sprintf(id, "button-%lu", m_buttons.size());
+  std::snprintf(id, sizeof(id), "button-%lu", m_buttons.size());
   button->setId(id);
   button->Click.connect([this, button]{ closeWindow(button); });
 
diff --git a/src/ui/entry.cpp b/src/ui/entry.cpp
index b70311b50..00a5f78eb 100644
--- a/src/ui/entry.cpp
+++ b/src/ui/entry.cpp
@@ -60,7 +60,7 @@ Entry::Entry(const int maxsize, const char* format, ...)
   if (format) {
     va_list ap;
     va_start(ap, format);
-    vsprintf(buf, format, ap);
+    std::vsnprintf(buf, sizeof(buf), format, ap);
     va_end(ap);
   }
   // empty string
diff --git a/src/ui/slider.cpp b/src/ui/slider.cpp
index a6c0bf014..5dbe1d4e9 100644
--- a/src/ui/slider.cpp
+++ b/src/ui/slider.cpp
@@ -74,7 +74,7 @@ std::string Slider::convertValueToText(int value) const
     return m_delegate->onGetTextFromValue(value);
   else {
     char buf[128];
-    std::sprintf(buf, "%d", value);
+    std::snprintf(buf, sizeof(buf), "%d", value);
     return buf;
   }
 }
diff --git a/src/ui/widget.cpp b/src/ui/widget.cpp
index acfe8aa75..7095f1db0 100644
--- a/src/ui/widget.cpp
+++ b/src/ui/widget.cpp
@@ -144,7 +144,7 @@ void Widget::setTextf(const char *format, ...)
     va_list ap;
     va_start(ap, format);
     char buf[4096];
-    vsprintf(buf, format, ap);
+    std::vsnprintf(buf, sizeof(buf), format, ap);
     va_end(ap);
 
     setText(buf);