diff --git a/docs/metadata/data_structures/message.rst b/docs/metadata/data_structures/message.rst
index c0600caa..1d74ee3a 100644
--- a/docs/metadata/data_structures/message.rst
+++ b/docs/metadata/data_structures/message.rst
@@ -37,7 +37,7 @@ Messages are given as key-value maps.
 
   ``string list``
 
-  A list of CommonMark strings to be substituted into the message content string. The content string must use numbered specifiers (``%1%``, ``%2%``, etc.), where the numbers correspond to the position of the substitution string in this list to use, to denote where these strings are to be substituted.
+  A list of CommonMark strings to be substituted into the message content string. The content string must use numbered specifiers (``{0}``, ``{1}``, etc.), where the numbers correspond to the position of the substitution string in this list to use, to denote where these strings are to be substituted.
 
 .. _languages:
 
@@ -102,7 +102,7 @@ In English,
 .. code-block:: yaml
 
   type: say
-  content: 'A newer version of %1% [is available](%2%).'
+  content: 'A newer version of {0} [is available]({1}).'
   subs:
     - 'this plugin'
     - 'http://www.example.com'
diff --git a/src/api/helpers/crc.cpp b/src/api/helpers/crc.cpp
index 927a79a5..307b2d05 100644
--- a/src/api/helpers/crc.cpp
+++ b/src/api/helpers/crc.cpp
@@ -24,8 +24,9 @@
 
 #include "api/helpers/crc.h"
 
+#include <spdlog/fmt/fmt.h>
+
 #include <boost/crc.hpp>
-#include <boost/format.hpp>
 #include <fstream>
 
 #include "api/helpers/logging.h"
@@ -80,7 +81,5 @@ uint32_t GetCrc32(const std::filesystem::path& filename) {
   }
 }
 
-std::string CrcToString(uint32_t crc) {
-  return (boost::format("%08X") % crc).str();
-}
+std::string CrcToString(uint32_t crc) { return fmt::format("{:08X}", crc); }
 }
diff --git a/src/api/metadata/yaml/message.h b/src/api/metadata/yaml/message.h
index b13238f1..effb1f3e 100644
--- a/src/api/metadata/yaml/message.h
+++ b/src/api/metadata/yaml/message.h
@@ -26,9 +26,10 @@
 
 #define YAML_CPP_SUPPORT_MERGE_KEYS
 
+#include <spdlog/fmt/bundled/args.h>
+#include <spdlog/fmt/fmt.h>
 #include <yaml-cpp/yaml.h>
 
-#include <boost/format.hpp>
 #include <string>
 #include <vector>
 
@@ -103,16 +104,17 @@ struct convert<loot::Message> {
     if (node["subs"]) {
       std::vector<std::string> subs =
           node["subs"].as<std::vector<std::string>>();
+
+      fmt::dynamic_format_arg_store<fmt::format_context> formatArgStore;
+      for (const auto& sub : subs) {
+        formatArgStore.push_back(sub);
+      }
+
       for (auto& mc : content) {
-        boost::format f(mc.GetText());
-
-        for (const auto& sub : subs) {
-          f = f % sub;
-        }
-
         try {
-          mc = loot::MessageContent(f.str(), mc.GetLanguage());
-        } catch (const boost::io::format_error& e) {
+          const auto text = fmt::vformat(mc.GetText(), formatArgStore);
+          mc = loot::MessageContent(text, mc.GetLanguage());
+        } catch (const fmt::format_error& e) {
           throw RepresentationException(
               node.Mark(),
               std::string("bad conversion: content substitution error: ") +
diff --git a/src/tests/api/internals/metadata/message_test.h b/src/tests/api/internals/metadata/message_test.h
index 226465de..0a6e4d8d 100644
--- a/src/tests/api/internals/metadata/message_test.h
+++ b/src/tests/api/internals/metadata/message_test.h
@@ -615,7 +615,7 @@ TEST_P(
     decodingFromYamlShouldApplySubstitutionsWhenThereIsOnlyOneContentString) {
   YAML::Node node = YAML::Load(
       "type: say\n"
-      "content: con%1%tent1\n"
+      "content: con{0}tent1\n"
       "subs:\n"
       "  - sub1");
   Message message = node.as<Message>();
@@ -630,9 +630,9 @@ TEST_P(MessageTest,
       "type: say\n"
       "content:\n"
       "  - lang: en\n"
-      "    text: content1 %1%\n"
+      "    text: content1 {0}\n"
       "  - lang: fr\n"
-      "    text: content2 %1%\n"
+      "    text: content2 {0}\n"
       "subs:\n"
       "  - sub");
   Message message = node.as<Message>();
@@ -649,7 +649,7 @@ TEST_P(
     decodingFromYamlShouldThrowIfTheContentStringExpectsMoreSubstitutionsThanExist) {
   YAML::Node node = YAML::Load(
       "type: say\n"
-      "content: '%1% %2%'\n"
+      "content: '{0} {1}'\n"
       "subs:\n"
       "  - sub1");
 
@@ -662,10 +662,10 @@ TEST_P(MessageTest,
        decodingFromYamlShouldIgnoreSubstitutionSyntaxIfNoSubstitutionsExist) {
   YAML::Node node = YAML::Load(
       "type: say\n"
-      "content: con%1%tent1\n");
+      "content: con{0}tent1\n");
   Message message = node.as<Message>();
 
-  EXPECT_EQ(MessageContents({MessageContent("con%1%tent1")}),
+  EXPECT_EQ(MessageContents({MessageContent("con{0}tent1")}),
             message.GetContent());
 }