diff --git a/src/format/format.cpp b/src/format/format.cpp
index 68516de..1be57dc 100644
--- a/src/format/format.cpp
+++ b/src/format/format.cpp
@@ -1,11 +1,71 @@
+#include "format/format.hpp"
 #include "markdown/markdown.hpp"
 #include <string>
 
-static bool replace_once(std::string &str, const std::string &from,
-                         const std::string &to) {
-  size_t start_pos = str.find(from);
-  if (start_pos == std::string::npos)
+// Remove everything from START to STOP
+static bool remove_from_to(std::string &STR, const std::string &START,
+                           const std::string &STOP) {
+  size_t start_pos = STR.find(START);
+  if (start_pos == std::string::npos) {
     return false;
-  str.replace(start_pos, from.length(), to);
+  }
+
+  size_t stop_pos = STR.find(STOP, start_pos);
+  if (stop_pos == std::string::npos) {
+    return false;
+  }
+
+  STR.replace(start_pos, stop_pos - start_pos + STOP.length(), "");
   return true;
 }
+
+std::string format_file(const std::string &TEMPLATE_FILE,
+                        const std::string &TEMPLATE, const std::string &INPUT) {
+  std::string result = TEMPLATE_FILE;
+  size_t current_pos = 0;
+
+  while (true) {
+    size_t found_pos = result.find(TEMPLATE, current_pos);
+
+    if (found_pos == std::string::npos) {
+      break;
+    }
+
+    result.replace(found_pos, TEMPLATE.length(), INPUT);
+    current_pos = found_pos + INPUT.length();
+  }
+  return result;
+}
+
+std::string format_file_conditionally(const std::string &TEMPLATE_FILE,
+                                      const std::string &START_TAG,
+                                      const std::string &END_TAG,
+                                      const std::string &TEMPLATE,
+                                      const std::string &INPUT) {
+  std::string result = TEMPLATE_FILE;
+
+  if (INPUT.empty()) {
+    while (true) {
+      if (!remove_from_to(result, START_TAG, END_TAG)) {
+        break;
+      }
+    }
+  } else {
+    // remove START tag
+    size_t pos = 0;
+    while ((pos = result.find(START_TAG, pos)) != std::string::npos) {
+      result.replace(pos, START_TAG.length(), "");
+    }
+
+    // remove END tag
+    pos = 0;
+    while ((pos = result.find(END_TAG, pos)) != std::string::npos) {
+      result.replace(pos, END_TAG.length(), "");
+    }
+
+    // replace
+    result = format_file(result, TEMPLATE, INPUT);
+  }
+
+  return result;
+}
diff --git a/src/format/format.hpp b/src/format/format.hpp
index ee70c95..78bf316 100644
--- a/src/format/format.hpp
+++ b/src/format/format.hpp
@@ -1,7 +1,21 @@
 #include <string>
 
-// Change template from file into html
-// Return html in string
-std::string inject_html_into_template(const std::string &FILE_NAME,
+// @brief Format file.
+// @param TEMPLATE_FILE File that you want to format in string.
+// @param TEMPLATE Template that you want to replace. For example `{{title}}`
+// @param INPUT Text that you want to replace TEMPLATE with.
+// @return Formatted file in std::string
+std::string format_file(const std::string &TEMPLATE_FILE,
+                        const std::string &TEMPLATE, const std::string &INPUT);
+
+// @brief Format file conditionally. Replace everything between `{{if
+// _something_}}` to `{{endif}}` If INPUT is empty then everything between
+// this will be removed.
+// @param TEMPLATE_FILE File that you want to format in string.
+// @param TEMPLATE Full name of the if statement. For example `{{if title}}`
+// @return Formatted file in std::string
+std::string format_file_conditionally(const std::string &TEMPLATE_FILE,
+                                      const std::string &START_TAG,
+                                      const std::string &END_TAG,
                                       const std::string &TEMPLATE,
-                                      const std::string &HTML);
+                                      const std::string &INPUT);
diff --git a/src/tests.cpp b/src/tests.cpp
index e13575e..c2bc76d 100644
--- a/src/tests.cpp
+++ b/src/tests.cpp
@@ -31,6 +31,58 @@ constexpr const char *formatter_html = R"(<!DOCTYPE html>
 </body>
 </html>)";
 
+constexpr const char *formated_html = R"(<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Document</title>
+</head>
+<body>
+    I'm formatted!
+</body>
+</html>)";
+
+constexpr const char *formatter_html_conditionally = R"(<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Document</title>
+</head>
+<body>
+{{if tag}}
+    <p>{{tag}}</p>
+{{endif}}
+</body>
+</html>)";
+
+constexpr const char *formated_html_conditionally = R"(<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Document</title>
+</head>
+<body>
+
+    <p>tag</p>
+
+</body>
+</html>)";
+
+constexpr const char *formated_html_conditionally_empty = R"(<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Document</title>
+</head>
+<body>
+
+</body>
+</html>)";
+
 constexpr const char *no_metadata_post_md = R"(# This markdown has no metadata.
 That's bad. Don't do it. It's for tests only.)";
 
@@ -88,6 +140,8 @@ TEST_CASE("Test reading a file that doesn't exist") {
   REQUIRE_THROWS(read_file("this/path/doesnt/exist"));
 }
 
+// Config tests
+
 TEST_CASE("Checking config file read", "[config]") {
   Config config = get_config(TestFiles::config_toml);
 
@@ -98,6 +152,8 @@ TEST_CASE("Checking config file read", "[config]") {
   REQUIRE(config.general.title == "Blog");
 }
 
+// Markdown tests
+
 TEST_CASE("get_metadata function data correctness test") {
   Metadata result = get_metadata(TestFiles::post_md).value();
 
@@ -160,3 +216,28 @@ int main() {
 
   REQUIRE(get_html(TestFiles::post_md) == EXPECTED_OUTPUT);
 }
+
+// Format tests
+TEST_CASE("Test format_file function with correct data") {
+  REQUIRE(TestFiles::formated_html == format_file(TestFiles::formatter_html,
+                                                  "{{replace_me}}",
+                                                  "I'm formatted!"));
+}
+
+TEST_CASE("Test format_file function with no templates") {
+  REQUIRE(TestFiles::formated_html ==
+          format_file(TestFiles::formated_html, "{{replace_me}}", "nothing"));
+}
+
+TEST_CASE("Test format_file_conditionally with tag") {
+  REQUIRE(TestFiles::formated_html_conditionally ==
+          format_file_conditionally(TestFiles::formatter_html_conditionally,
+                                    "{{if tag}}", "{{endif}}", "{{tag}}",
+                                    "tag"));
+}
+
+TEST_CASE("Test format_file_conditionally with empty tag") {
+  REQUIRE(TestFiles::formated_html_conditionally_empty ==
+          format_file_conditionally(TestFiles::formatter_html_conditionally,
+                                    "{{if tag}}", "{{endif}}", "{{tag}}", ""));
+}