diff --git a/tests/test_cli.py b/tests/test_cli.py
index 241e0f4a..444f2f9e 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -286,8 +286,8 @@ def test_run_with_implicit_extends_config(self):
 
         with RunContext(self) as ctx:
             cli.run(('-d', 'default', '-f', 'parsable', path))
-        expected_out = ('%s:1:1: [warning] missing document start "---" '
-                        '(document-start)\n' % path)
+        expected_out = (f'{path}:1:1: [warning] missing document start "---" '
+                        f'(document-start)\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (0, expected_out, ''))
 
@@ -424,9 +424,9 @@ def test_run_one_problem_file(self):
             cli.run(('-f', 'parsable', path))
         self.assertEqual(ctx.returncode, 1)
         self.assertEqual(ctx.stdout, (
-            '%s:2:4: [error] trailing spaces (trailing-spaces)\n'
-            '%s:3:4: [error] no new line character at the end of file '
-            '(new-line-at-end-of-file)\n' % (path, path)))
+            f'{path}:2:4: [error] trailing spaces (trailing-spaces)\n'
+            f'{path}:3:4: [error] no new line character at the end of file '
+            f'(new-line-at-end-of-file)\n'))
         self.assertEqual(ctx.stderr, '')
 
     def test_run_one_warning(self):
@@ -476,8 +476,8 @@ def test_run_multiple_files(self):
             cli.run(['-f', 'parsable'] + items)
         self.assertEqual((ctx.returncode, ctx.stderr), (1, ''))
         self.assertEqual(ctx.stdout, (
-            '%s:3:1: [error] duplication of key "key" in mapping '
-            '(key-duplicates)\n') % path)
+            f'{path}:3:1: [error] duplication of key "key" in mapping '
+            f'(key-duplicates)\n'))
 
     def test_run_piped_output_nocolor(self):
         path = os.path.join(self.wd, 'a.yaml')
@@ -486,11 +486,11 @@ def test_run_piped_output_nocolor(self):
             cli.run((path, ))
         self.assertEqual((ctx.returncode, ctx.stderr), (1, ''))
         self.assertEqual(ctx.stdout, (
-            '%s\n'
-            '  2:4       error    trailing spaces  (trailing-spaces)\n'
-            '  3:4       error    no new line character at the end of file  '
-            '(new-line-at-end-of-file)\n'
-            '\n' % path))
+            f'{path}\n'
+            f'  2:4       error    trailing spaces  (trailing-spaces)\n'
+            f'  3:4       error    no new line character at the end of file  '
+            f'(new-line-at-end-of-file)\n'
+            f'\n'))
 
     def test_run_default_format_output_in_tty(self):
         path = os.path.join(self.wd, 'a.yaml')
@@ -517,13 +517,13 @@ def test_run_default_format_output_in_tty(self):
         output.close()
 
         self.assertEqual(out, (
-            '\033[4m%s\033[0m\n'
-            '  \033[2m2:4\033[0m       \033[31merror\033[0m    '
-            'trailing spaces  \033[2m(trailing-spaces)\033[0m\n'
-            '  \033[2m3:4\033[0m       \033[31merror\033[0m    '
-            'no new line character at the end of file  '
-            '\033[2m(new-line-at-end-of-file)\033[0m\n'
-            '\n' % path))
+            f'\033[4m{path}\033[0m\n'
+            f'  \033[2m2:4\033[0m       \033[31merror\033[0m    '
+            f'trailing spaces  \033[2m(trailing-spaces)\033[0m\n'
+            f'  \033[2m3:4\033[0m       \033[31merror\033[0m    '
+            f'no new line character at the end of file  '
+            f'\033[2m(new-line-at-end-of-file)\033[0m\n'
+            f'\n'))
 
     def test_run_default_format_output_without_tty(self):
         path = os.path.join(self.wd, 'a.yaml')
@@ -531,11 +531,11 @@ def test_run_default_format_output_without_tty(self):
         with RunContext(self) as ctx:
             cli.run((path, ))
         expected_out = (
-            '%s\n'
-            '  2:4       error    trailing spaces  (trailing-spaces)\n'
-            '  3:4       error    no new line character at the end of file  '
-            '(new-line-at-end-of-file)\n'
-            '\n' % path)
+            f'{path}\n'
+            f'  2:4       error    trailing spaces  (trailing-spaces)\n'
+            f'  3:4       error    no new line character at the end of file  '
+            f'(new-line-at-end-of-file)\n'
+            f'\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
@@ -545,11 +545,11 @@ def test_run_auto_output_without_tty_output(self):
         with RunContext(self) as ctx:
             cli.run((path, '--format', 'auto'))
         expected_out = (
-            '%s\n'
-            '  2:4       error    trailing spaces  (trailing-spaces)\n'
-            '  3:4       error    no new line character at the end of file  '
-            '(new-line-at-end-of-file)\n'
-            '\n' % path)
+            f'{path}\n'
+            f'  2:4       error    trailing spaces  (trailing-spaces)\n'
+            f'  3:4       error    no new line character at the end of file  '
+            f'(new-line-at-end-of-file)\n'
+            f'\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
@@ -559,13 +559,13 @@ def test_run_format_colored(self):
         with RunContext(self) as ctx:
             cli.run((path, '--format', 'colored'))
         expected_out = (
-            '\033[4m%s\033[0m\n'
-            '  \033[2m2:4\033[0m       \033[31merror\033[0m    '
-            'trailing spaces  \033[2m(trailing-spaces)\033[0m\n'
-            '  \033[2m3:4\033[0m       \033[31merror\033[0m    '
-            'no new line character at the end of file  '
-            '\033[2m(new-line-at-end-of-file)\033[0m\n'
-            '\n' % path)
+            f'\033[4m{path}\033[0m\n'
+            f'  \033[2m2:4\033[0m       \033[31merror\033[0m    '
+            f'trailing spaces  \033[2m(trailing-spaces)\033[0m\n'
+            f'  \033[2m3:4\033[0m       \033[31merror\033[0m    '
+            f'no new line character at the end of file  '
+            f'\033[2m(new-line-at-end-of-file)\033[0m\n'
+            f'\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
@@ -575,10 +575,10 @@ def test_run_format_colored_warning(self):
         with RunContext(self) as ctx:
             cli.run((path, '--format', 'colored'))
         expected_out = (
-            '\033[4m%s\033[0m\n'
-            '  \033[2m1:1\033[0m       \033[33mwarning\033[0m  '
-            'missing document start "---"  \033[2m(document-start)\033[0m\n'
-            '\n' % path)
+            f'\033[4m{path}\033[0m\n'
+            f'  \033[2m1:1\033[0m       \033[33mwarning\033[0m  '
+            f'missing document start "---"  \033[2m(document-start)\033[0m\n'
+            f'\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (0, expected_out, ''))
 
@@ -588,13 +588,12 @@ def test_run_format_github(self):
         with RunContext(self) as ctx:
             cli.run((path, '--format', 'github'))
         expected_out = (
-            '::group::%s\n'
-            '::error file=%s,line=2,col=4::2:4 [trailing-spaces] trailing'
-            ' spaces\n'
-            '::error file=%s,line=3,col=4::3:4 [new-line-at-end-of-file] no'
-            ' new line character at the end of file\n'
-            '::endgroup::\n\n'
-            % (path, path, path))
+            f'::group::{path}\n'
+            f'::error file={path},line=2,col=4::2:4 [trailing-spaces] trailing'
+            f' spaces\n'
+            f'::error file={path},line=3,col=4::3:4 [new-line-at-end-of-file]'
+            f' no new line character at the end of file\n'
+            f'::endgroup::\n\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
@@ -608,13 +607,12 @@ def test_github_actions_detection(self):
             os.environ['GITHUB_WORKFLOW'] = 'something'
             cli.run((path, ))
         expected_out = (
-            '::group::%s\n'
-            '::error file=%s,line=2,col=4::2:4 [trailing-spaces] trailing'
-            ' spaces\n'
-            '::error file=%s,line=3,col=4::3:4 [new-line-at-end-of-file] no'
-            ' new line character at the end of file\n'
-            '::endgroup::\n\n'
-            % (path, path, path))
+            f'::group::{path}\n'
+            f'::error file={path},line=2,col=4::2:4 [trailing-spaces] trailing'
+            f' spaces\n'
+            f'::error file={path},line=3,col=4::3:4 [new-line-at-end-of-file]'
+            f' no new line character at the end of file\n'
+            f'::endgroup::\n\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
@@ -640,11 +638,11 @@ def test_run_no_warnings(self):
         with RunContext(self) as ctx:
             cli.run((path, '--no-warnings', '-f', 'auto'))
         expected_out = (
-            '%s\n'
-            '  2:4       error    trailing spaces  (trailing-spaces)\n'
-            '  3:4       error    no new line character at the end of file  '
-            '(new-line-at-end-of-file)\n'
-            '\n' % path)
+            f'{path}\n'
+            f'  2:4       error    trailing spaces  (trailing-spaces)\n'
+            f'  3:4       error    no new line character at the end of file  '
+            f'(new-line-at-end-of-file)\n'
+            f'\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
@@ -671,10 +669,10 @@ def test_run_non_universal_newline(self):
         with RunContext(self) as ctx:
             cli.run(('-d', 'rules:\n  new-lines:\n    type: unix', path))
         expected_out = (
-            '%s\n'
-            '  1:4       error    wrong new line character: expected \\n'
-            '  (new-lines)\n'
-            '\n' % path)
+            f'{path}\n'
+            f'  1:4       error    wrong new line character: expected \\n'
+            f'  (new-lines)\n'
+            f'\n')
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
diff --git a/tests/test_spec_examples.py b/tests/test_spec_examples.py
index c04e3995..ac68e12e 100644
--- a/tests/test_spec_examples.py
+++ b/tests/test_spec_examples.py
@@ -39,7 +39,7 @@
 #             text = text.replace('\u21d4', '')    # byte order mark
 #             text = text.replace('\u2192', '\t')  # right arrow
 #             text = text.replace('\u00b0', '')    # empty scalar
-#             with open('tests/yaml-1.2-spec-examples/%s' % id, 'w',
+#             with open(f'tests/yaml-1.2-spec-examples/{id}', 'w',
 #                       encoding='utf-8') as g:
 #                 g.write(text)
 
diff --git a/yamllint/cli.py b/yamllint/cli.py
index d7fa1561..604e5940 100644
--- a/yamllint/cli.py
+++ b/yamllint/cli.py
@@ -49,52 +49,41 @@ def supports_color():
 class Format:
     @staticmethod
     def parsable(problem, filename):
-        return ('%(file)s:%(line)s:%(column)s: [%(level)s] %(message)s' %
-                {'file': filename,
-                 'line': problem.line,
-                 'column': problem.column,
-                 'level': problem.level,
-                 'message': problem.message})
+        return (f'{filename}:{problem.line}:{problem.column}: '
+                f'[{problem.level}] {problem.message}')
 
     @staticmethod
     def standard(problem, filename):
-        line = '  %d:%d' % (problem.line, problem.column)
+        line = f'  {problem.line}:{problem.column}'
         line += max(12 - len(line), 0) * ' '
         line += problem.level
         line += max(21 - len(line), 0) * ' '
         line += problem.desc
         if problem.rule:
-            line += '  (%s)' % problem.rule
+            line += f'  ({problem.rule})'
         return line
 
     @staticmethod
     def standard_color(problem, filename):
-        line = '  \033[2m%d:%d\033[0m' % (problem.line, problem.column)
+        line = f'  \033[2m{problem.line}:{problem.column}\033[0m'
         line += max(20 - len(line), 0) * ' '
         if problem.level == 'warning':
-            line += '\033[33m%s\033[0m' % problem.level
+            line += f'\033[33m{problem.level}\033[0m'
         else:
-            line += '\033[31m%s\033[0m' % problem.level
+            line += f'\033[31m{problem.level}\033[0m'
         line += max(38 - len(line), 0) * ' '
         line += problem.desc
         if problem.rule:
-            line += '  \033[2m(%s)\033[0m' % problem.rule
+            line += f'  \033[2m({problem.rule})\033[0m'
         return line
 
     @staticmethod
     def github(problem, filename):
-        line = '::'
-        line += problem.level
-        line += ' file=' + filename + ','
-        line += 'line=' + format(problem.line) + ','
-        line += 'col=' + format(problem.column)
-        line += '::'
-        line += format(problem.line)
-        line += ':'
-        line += format(problem.column)
-        line += ' '
+        line = f'::{problem.level} file={format(filename)},' \
+               f'line={format(problem.line)},col={format(problem.column)}' \
+               f'::{format(problem.line)}:{format(problem.column)} '
         if problem.rule:
-            line += '[' + problem.rule + '] '
+            line += f'[{problem.rule}] '
         line += problem.desc
         return line
 
@@ -118,12 +107,12 @@ def show_problems(problems, file, args_format, no_warn):
             print(Format.parsable(problem, file))
         elif args_format == 'github':
             if first:
-                print('::group::%s' % file)
+                print(f'::group::{file}')
                 first = False
             print(Format.github(problem, file))
         elif args_format == 'colored':
             if first:
-                print('\033[4m%s\033[0m' % file)
+                print(f'\033[4m{file}\033[0m')
                 first = False
             print(Format.standard_color(problem, file))
         else:
@@ -184,7 +173,7 @@ def run(argv=None):
                         action='store_true',
                         help='output only error level problems')
     parser.add_argument('-v', '--version', action='version',
-                        version='{} {}'.format(APP_NAME, APP_VERSION))
+                        version=f'{APP_NAME} {APP_VERSION}')
 
     args = parser.parse_args(argv)
 
@@ -202,7 +191,7 @@ def run(argv=None):
     try:
         if args.config_data is not None:
             if args.config_data != '' and ':' not in args.config_data:
-                args.config_data = 'extends: ' + args.config_data
+                args.config_data = f'extends: {args.config_data}'
             conf = YamlLintConfig(content=args.config_data)
         elif args.config_file is not None:
             conf = YamlLintConfig(file=args.config_file)
diff --git a/yamllint/config.py b/yamllint/config.py
index a5ef405e..47a61a86 100644
--- a/yamllint/config.py
+++ b/yamllint/config.py
@@ -76,7 +76,7 @@ def parse(self, raw_content):
         try:
             conf = yaml.safe_load(raw_content)
         except Exception as e:
-            raise YamlLintConfigError('invalid config: %s' % e)
+            raise YamlLintConfigError(f'invalid config: {e}')
 
         if not isinstance(conf, dict):
             raise YamlLintConfigError('invalid config: not a dict')
@@ -95,7 +95,7 @@ def parse(self, raw_content):
             try:
                 self.extend(base)
             except Exception as e:
-                raise YamlLintConfigError('invalid config: %s' % e)
+                raise YamlLintConfigError(f'invalid config: {e}')
 
         if 'ignore' in conf and 'ignore-from-file' in conf:
             raise YamlLintConfigError(
@@ -143,7 +143,7 @@ def validate(self):
             try:
                 rule = yamllint.rules.get(id)
             except Exception as e:
-                raise YamlLintConfigError('invalid config: %s' % e)
+                raise YamlLintConfigError(f'invalid config: {e}')
 
             self.rules[id] = validate_rule_conf(rule, self.rules[id])
 
@@ -179,16 +179,16 @@ def validate_rule_conf(rule, conf):
                 continue
             if optkey not in options:
                 raise YamlLintConfigError(
-                    'invalid config: unknown option "%s" for rule "%s"' %
-                    (optkey, rule.ID))
+                    f'invalid config: unknown option "{optkey}" for rule '
+                    f'"{rule.ID}"')
             # Example: CONF = {option: (bool, 'mixed')}
             #          → {option: true}         → {option: mixed}
             if isinstance(options[optkey], tuple):
                 if (conf[optkey] not in options[optkey] and
                         type(conf[optkey]) not in options[optkey]):
                     raise YamlLintConfigError(
-                        'invalid config: option "%s" of "%s" should be in %s'
-                        % (optkey, rule.ID, options[optkey]))
+                        f'invalid config: option "{optkey}" of "{rule.ID}" '
+                        f'should be in {options[optkey]}')
             # Example: CONF = {option: ['flag1', 'flag2', int]}
             #          → {option: [flag1]}      → {option: [42, flag1, flag2]}
             elif isinstance(options[optkey], list):
@@ -197,16 +197,15 @@ def validate_rule_conf(rule, conf):
                             type(flag) not in options[optkey]
                             for flag in conf[optkey])):
                     raise YamlLintConfigError(
-                        ('invalid config: option "%s" of "%s" should only '
-                         'contain values in %s')
-                        % (optkey, rule.ID, str(options[optkey])))
+                        f'invalid config: option "{optkey}" of "{rule.ID}" '
+                        f'should only contain values in {options[optkey]}')
             # Example: CONF = {option: int}
             #          → {option: 42}
             else:
                 if not isinstance(conf[optkey], options[optkey]):
                     raise YamlLintConfigError(
-                        'invalid config: option "%s" of "%s" should be %s'
-                        % (optkey, rule.ID, options[optkey].__name__))
+                        f'invalid config: option "{optkey}" of "{rule.ID}" '
+                        f'should be {options[optkey].__name__}')
         for optkey in options:
             if optkey not in conf:
                 conf[optkey] = options_default[optkey]
@@ -214,12 +213,11 @@ def validate_rule_conf(rule, conf):
         if hasattr(rule, 'VALIDATE'):
             res = rule.VALIDATE(conf)
             if res:
-                raise YamlLintConfigError('invalid config: %s: %s' %
-                                          (rule.ID, res))
+                raise YamlLintConfigError(f'invalid config: {rule.ID}: {res}')
     else:
-        raise YamlLintConfigError(('invalid config: rule "%s": should be '
-                                   'either "enable", "disable" or a dict')
-                                  % rule.ID)
+        raise YamlLintConfigError(
+            f'invalid config: rule "{rule.ID}": should be either "enable", '
+            f'"disable" or a dict')
 
     return conf
 
@@ -228,7 +226,7 @@ def get_extended_config_file(name):
     # Is it a standard conf shipped with yamllint...
     if '/' not in name:
         std_conf = os.path.join(os.path.dirname(os.path.realpath(__file__)),
-                                'conf', name + '.yaml')
+                                'conf', f'{name}.yaml')
 
         if os.path.isfile(std_conf):
             return std_conf
diff --git a/yamllint/linter.py b/yamllint/linter.py
index 5501bb59..0de1f716 100644
--- a/yamllint/linter.py
+++ b/yamllint/linter.py
@@ -50,7 +50,7 @@ def __init__(self, line, column, desc='<no description>', rule=None):
     @property
     def message(self):
         if self.rule is not None:
-            return '{} ({})'.format(self.desc, self.rule)
+            return f'{self.desc} ({self.rule})'
         return self.desc
 
     def __eq__(self, other):
@@ -63,7 +63,7 @@ def __lt__(self, other):
                 (self.line == other.line and self.column < other.column))
 
     def __repr__(self):
-        return '%d:%d: %s' % (self.line, self.column, self.message)
+        return f'{self.line}:{self.column}: {self.message}'
 
 
 def get_cosmetic_problems(buffer, conf, filepath):
diff --git a/yamllint/rules/__init__.py b/yamllint/rules/__init__.py
index 6b5e4467..606b37a4 100644
--- a/yamllint/rules/__init__.py
+++ b/yamllint/rules/__init__.py
@@ -68,6 +68,6 @@
 
 def get(id):
     if id not in _RULES:
-        raise ValueError('no such rule: "%s"' % id)
+        raise ValueError(f'no such rule: "{id}"')
 
     return _RULES[id]
diff --git a/yamllint/rules/empty_lines.py b/yamllint/rules/empty_lines.py
index 73a9fd1e..eca78125 100644
--- a/yamllint/rules/empty_lines.py
+++ b/yamllint/rules/empty_lines.py
@@ -113,5 +113,5 @@ def check(conf, line):
             max = conf['max-end']
 
         if blank_lines > max:
-            yield LintProblem(line.line_no, 1, 'too many blank lines (%d > %d)'
-                                               % (blank_lines, max))
+            yield LintProblem(line.line_no, 1,
+                              f'too many blank lines ({blank_lines} > {max})')
diff --git a/yamllint/rules/indentation.py b/yamllint/rules/indentation.py
index e63a733a..d839d5aa 100644
--- a/yamllint/rules/indentation.py
+++ b/yamllint/rules/indentation.py
@@ -227,7 +227,7 @@ def __init__(self, type, indent, line_indent=None):
         self.implicit_block_seq = False
 
     def __repr__(self):
-        return '%s:%d' % (labels[self.type], self.indent)
+        return f'{labels[self.type]}:{self.indent}'
 
 
 def check_scalar_indentation(conf, token, context):
@@ -303,8 +303,8 @@ def detect_indent(base_indent):
 
         if indent != expected_indent:
             yield LintProblem(line_no, indent + 1,
-                              'wrong indentation: expected %d but found %d' %
-                              (expected_indent, indent))
+                              f'wrong indentation: expected {expected_indent}'
+                              f'but found {indent}')
 
 
 def _check(conf, token, prev, next, nextnext, context):
@@ -342,11 +342,11 @@ def detect_indent(base_indent, next):
 
         if found_indentation != expected:
             if expected < 0:
-                message = 'wrong indentation: expected at least %d' % \
-                          (found_indentation + 1)
+                message = f'wrong indentation: expected at least ' \
+                          f'{found_indentation + 1}'
             else:
-                message = 'wrong indentation: expected %d but found %d' % \
-                          (expected, found_indentation)
+                message = f'wrong indentation: expected {expected} but ' \
+                          f'found {found_indentation}'
             yield LintProblem(token.start_mark.line + 1,
                               found_indentation + 1, message)
 
diff --git a/yamllint/rules/key_duplicates.py b/yamllint/rules/key_duplicates.py
index 3f93e7dc..771a8e2a 100644
--- a/yamllint/rules/key_duplicates.py
+++ b/yamllint/rules/key_duplicates.py
@@ -95,6 +95,6 @@ def check(conf, token, prev, next, nextnext, context):
                     next.value != '<<'):
                 yield LintProblem(
                     next.start_mark.line + 1, next.start_mark.column + 1,
-                    'duplication of key "%s" in mapping' % next.value)
+                    f'duplication of key "{next.value}" in mapping')
             else:
                 context['stack'][-1].keys.append(next.value)
diff --git a/yamllint/rules/key_ordering.py b/yamllint/rules/key_ordering.py
index ad38ed71..7fa9597a 100644
--- a/yamllint/rules/key_ordering.py
+++ b/yamllint/rules/key_ordering.py
@@ -122,6 +122,6 @@ def check(conf, token, prev, next, nextnext, context):
                    for key in context['stack'][-1].keys):
                 yield LintProblem(
                     next.start_mark.line + 1, next.start_mark.column + 1,
-                    'wrong ordering of key "%s" in mapping' % next.value)
+                    f'wrong ordering of key "{next.value}" in mapping')
             else:
                 context['stack'][-1].keys.append(next.value)
diff --git a/yamllint/rules/octal_values.py b/yamllint/rules/octal_values.py
index 7796e505..eb24c81f 100644
--- a/yamllint/rules/octal_values.py
+++ b/yamllint/rules/octal_values.py
@@ -99,8 +99,7 @@ def check(conf, token, prev, next, nextnext, context):
                         IS_OCTAL_NUMBER_PATTERN.match(val[1:])):
                     yield LintProblem(
                         token.start_mark.line + 1, token.end_mark.column + 1,
-                        'forbidden implicit octal value "%s"' %
-                        token.value)
+                        f'forbidden implicit octal value "{token.value}"')
 
     if conf['forbid-explicit-octal']:
         if isinstance(token, yaml.tokens.ScalarToken):
@@ -110,5 +109,4 @@ def check(conf, token, prev, next, nextnext, context):
                         IS_OCTAL_NUMBER_PATTERN.match(val[2:])):
                     yield LintProblem(
                         token.start_mark.line + 1, token.end_mark.column + 1,
-                        'forbidden explicit octal value "%s"' %
-                        token.value)
+                        f'forbidden explicit octal value "{token.value}"')
diff --git a/yamllint/rules/quoted_strings.py b/yamllint/rules/quoted_strings.py
index e4c86f16..9380ae57 100644
--- a/yamllint/rules/quoted_strings.py
+++ b/yamllint/rules/quoted_strings.py
@@ -240,7 +240,7 @@ def check(conf, token, prev, next, nextnext, context):
         if (token.style is None or
             not (_quote_match(quote_type, token.style) or
                  (conf['allow-quoted-quotes'] and _has_quoted_quotes(token)))):
-            msg = "string value is not quoted with %s quotes" % quote_type
+            msg = f"string value is not quoted with {quote_type} quotes"
 
     elif conf['required'] is False:
 
@@ -249,7 +249,7 @@ def check(conf, token, prev, next, nextnext, context):
                 not _quote_match(quote_type, token.style) and
                 not (conf['allow-quoted-quotes'] and
                      _has_quoted_quotes(token))):
-            msg = "string value is not quoted with %s quotes" % quote_type
+            msg = f"string value is not quoted with {quote_type} quotes"
 
         elif not token.style:
             is_extra_required = any(re.search(r, token.value)
@@ -267,14 +267,14 @@ def check(conf, token, prev, next, nextnext, context):
             is_extra_allowed = any(re.search(r, token.value)
                                    for r in conf['extra-allowed'])
             if not (is_extra_required or is_extra_allowed):
-                msg = "string value is redundantly quoted with %s quotes" % (
-                    quote_type)
+                msg = f"string value is redundantly quoted with " \
+                      f"{quote_type} quotes"
 
         # But when used need to match config
         elif (token.style and
               not _quote_match(quote_type, token.style) and
               not (conf['allow-quoted-quotes'] and _has_quoted_quotes(token))):
-            msg = "string value is not quoted with %s quotes" % quote_type
+            msg = f"string value is not quoted with {quote_type} quotes"
 
         elif not token.style:
             is_extra_required = len(conf['extra-required']) and any(