diff --git a/include/export/adoc.hpp b/include/export/adoc.hpp
index 7eaf467..7d8a984 100644
--- a/include/export/adoc.hpp
+++ b/include/export/adoc.hpp
@@ -46,24 +46,30 @@ private:
     using replacemap = const std::map<const string, const string>;
 
     //! Replace strings in text.
+    [[nodiscard]]
     string replace(string text, const replacemap &replacements) const;
 
     //! Replaces characters in tags that asciidoctor doesn't like.
+    [[nodiscard]]
     string replace_in_tag(const string &text) const;
 
     //! Replaces characters in title that asciidoctor doesn't like.
+    [[nodiscard]]
     string replace_in_title(const string &text) const;
 
     //! Replaces characters in URI that asciidoctor doesn't like.
+    [[nodiscard]]
     string replace_in_uri(const string &text) const;
 
     //! Print things sorted by tag.
     void print_tags(const tagmap &tags) const;
 
     //! Get ISO-8601 day from Database::entry.
+    [[nodiscard]]
     string get_day(const Database::entry &entry) const;
 
     //! Get ISO-8601 time from Database::entry.
+    [[nodiscard]]
     string get_time(const Database::entry &entry) const;
 };
 } // namespace remwharead::Export
diff --git a/include/export/csv.hpp b/include/export/csv.hpp
index 8499835..7810185 100644
--- a/include/export/csv.hpp
+++ b/include/export/csv.hpp
@@ -40,6 +40,7 @@ namespace remwharead::Export
 
     private:
         //! replaces " with "".
+        [[nodiscard]]
         string quote(string field) const;
     };
 } // namespace remwharead::Export
diff --git a/include/export/export.hpp b/include/export/export.hpp
index 0ecf9e0..b4528ae 100644
--- a/include/export/export.hpp
+++ b/include/export/export.hpp
@@ -67,6 +67,7 @@ protected:
      *
      *  @return Sorted list of Database::entry.
      */
+    [[nodiscard]]
     list<Database::entry> sort_entries(list<Database::entry> entries) const;
 };
 } // namespace remwharead::Export
diff --git a/include/search.hpp b/include/search.hpp
index 25a4a6d..3a935b9 100644
--- a/include/search.hpp
+++ b/include/search.hpp
@@ -57,6 +57,7 @@ public:
      *
      *  @since  0.7.0
      */
+    [[nodiscard]]
     list<Database::entry> search_tags(const string &expression, bool is_re)
         const;
 
@@ -72,6 +73,7 @@ public:
      *
      *  @since  0.7.0
      */
+    [[nodiscard]]
     list<Database::entry> search_all(const string &expression, bool is_re)
         const;
 
@@ -89,6 +91,7 @@ public:
      *  @since  0.7.2
      */
     // TODO(tastytea): Think of something more elegant.
+    [[nodiscard]]
     list<Database::entry> search_all_threaded(const string &expression,
                                               bool is_re) const;
 
@@ -106,6 +109,7 @@ private:
      *
      *  @since  0.7.0
      */
+    [[nodiscard]]
     vector<vector<string>> parse_expression(const string &expression) const;
 
     /*!
@@ -113,6 +117,7 @@ private:
      *
      *  @since  0.7.0
      */
+    [[nodiscard]]
     inline string to_lowercase(const string &str) const;
 };
 } // namespace remwharead
diff --git a/include/sqlite.hpp b/include/sqlite.hpp
index d341683..f91cea9 100644
--- a/include/sqlite.hpp
+++ b/include/sqlite.hpp
@@ -75,6 +75,7 @@ public:
          *
          *  @since  0.6.0
          */
+        [[nodiscard]]
         string fulltext_oneline() const;
     };
 
@@ -104,6 +105,7 @@ public:
      *
      *  @since  0.6.0
      */
+    [[nodiscard]]
     list<entry> retrieve(const time_point &start = time_point(),
                          const time_point &end = system_clock::now()) const;
 
@@ -112,6 +114,7 @@ private:
     std::unique_ptr<Session> _session;
     bool _connected;
 
+    [[nodiscard]]
     fs::path get_data_home() const;
 };
 } // namespace remwharead
diff --git a/include/time.hpp b/include/time.hpp
index e5fdb84..ce696e4 100644
--- a/include/time.hpp
+++ b/include/time.hpp
@@ -36,6 +36,7 @@ using time_point = system_clock::time_point;
  *  @param  strtime Time string in ISO 8601 or SQLite format.
  *  @param  sqlite  Is the string in SQLite format?
  */
+[[nodiscard]]
 time_point string_to_timepoint(const string &strtime, bool sqlite = false);
 
 /*!
@@ -46,6 +47,7 @@ time_point string_to_timepoint(const string &strtime, bool sqlite = false);
  *  @param  time_point The std::chrono::system_clock::time_point.
  *  @param  sqlite     Is the string in SQLite format?
  */
+[[nodiscard]]
 string timepoint_to_string(const time_point &tp, bool sqlite = false);
 } // namespace remwharead
 
diff --git a/include/uri.hpp b/include/uri.hpp
index c317f74..8d2c5f1 100644
--- a/include/uri.hpp
+++ b/include/uri.hpp
@@ -94,13 +94,15 @@ public:
      *
      *  @since  0.6.0
      */
+    [[nodiscard]]
     html_extract get();
 
     /*!
      *  @brief  Save %URI in archive and return archive-URI.
      *
      *  @since  0.6.0
-     */
+    */
+    [[nodiscard]]
     archive_answer archive() const;
 
 protected:
@@ -111,6 +113,7 @@ protected:
      *
      *  @since  0.6.0
      */
+    [[nodiscard]]
     string make_request(const string &uri, bool archive = false) const;
 
     /*!
@@ -118,21 +121,24 @@ protected:
      *
      *  @since  0.6.0
      */
-    string extract_title(const string &html);
+    [[nodiscard]]
+    string extract_title(const string &html) const;
 
     /*!
      *  @brief  Extract the description from an HTML page.
      *
      *  @since  0.6.0
      */
-    string extract_description(const string &html);
+    [[nodiscard]]
+    string extract_description(const string &html) const;
 
     /*!
      *  @brief  Removes HTML tags and superflous spaces from an HTML page.
      *
      *  @since  0.6.0
      */
-    string strip_html(const string &html);
+    [[nodiscard]]
+    string strip_html(const string &html) const;
 
     /*!
      *  @brief  Remove HTML tags.
@@ -142,21 +148,24 @@ protected:
      *
      *  @since  0.6.0
      */
-    string remove_html_tags(const string &html, const string &tag = "");
+    [[nodiscard]]
+    string remove_html_tags(const string &html, const string &tag = "") const;
 
     /*!
      *  @brief  Convert HTML entities to UTF-8.
      *
      *  @since  0.6.0
      */
-    string unescape_html(string html);
+    [[nodiscard]]
+    string unescape_html(string html) const;
 
     /*!
      *  @brief  Replace newlines with spaces.
      *
      *  @since  0.6.0
      */
-    string remove_newlines(string text);
+    [[nodiscard]]
+    string remove_newlines(string text) const;
 
     /*!
      *  @brief  Set proxy server.
@@ -170,6 +179,7 @@ protected:
      *
      *  @since  0.8.5
      */
+    [[nodiscard]]
     string cut_text(const string &text, uint16_t n_chars) const;
 };
 } // namespace remwharead
diff --git a/src/lib/uri.cpp b/src/lib/uri.cpp
index c257dd0..4328b7b 100644
--- a/src/lib/uri.cpp
+++ b/src/lib/uri.cpp
@@ -224,7 +224,7 @@ string URI::make_request(const string &uri, bool archive) const
     }
 }
 
-string URI::extract_title(const string &html)
+string URI::extract_title(const string &html) const
 {
     const RegEx re_htmlfile(".*\\.(.?html?|xml|rss)$", RegEx::RE_CASELESS);
     if (_uri.substr(0, 4) == "http" || re_htmlfile.match(_uri))
@@ -241,7 +241,7 @@ string URI::extract_title(const string &html)
     return "";
 }
 
-string URI::extract_description(const string &html)
+string URI::extract_description(const string &html) const
 {
     const RegEx re_htmlfile(".*\\.(.?html?|xml|rss)$", RegEx::RE_CASELESS);
     if (_uri.substr(0, 4) == "http" || re_htmlfile.match(_uri))
@@ -259,7 +259,7 @@ string URI::extract_description(const string &html)
     return "";
 }
 
-string URI::strip_html(const string &html)
+string URI::strip_html(const string &html) const
 {
     string out;
 
@@ -280,7 +280,7 @@ string URI::strip_html(const string &html)
     return unescape_html(out);
 }
 
-string URI::remove_html_tags(const string &html, const string &tag)
+string URI::remove_html_tags(const string &html, const string &tag) const
 {
     // NOTE: I did this with regex_replace before, but libstdc++ segfaulted.
     string out;
@@ -318,7 +318,7 @@ string URI::remove_html_tags(const string &html, const string &tag)
     return out;
 }
 
-string URI::unescape_html(string html)
+string URI::unescape_html(string html) const
 {
     // Used to convert int to utf-8 char.
     std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> u8c;
@@ -642,7 +642,7 @@ archive_answer URI::archive() const
     return { false, "Unknown error.", "" };
 }
 
-string URI::remove_newlines(string text)
+string URI::remove_newlines(string text) const
 {
     size_t posn = 0;
     while ((posn = text.find('\n', posn)) != std::string::npos)