diff --git a/README.md b/README.md
index 3d3d204..937bfba 100644
--- a/README.md
+++ b/README.md
@@ -115,7 +115,7 @@ $ otag write id3 song.mp3
 | `pdf` | `.pdf` | The keywords field |
 | `office` | `.docx` `.xlsx` `.pptx` `.odt` `.ods` `.odp`, reading also `.doc` `.xls` `.ppt` | The description field |
 | `frontmatter` | `.md` `.txt` `.markdown` `.rst` | `projects`, `contexts`, `tags` and `note` keys of the YAML front matter |
-| `hash//` | Source code such as `.py` `.js` `.c` `.rs`, plus `.md` `.txt` | A `#// +project @context #tag note` line within the first five lines |
+| `comment` | Source code such as `.py` `.sh` `.toml` `.js` `.c` `.go` `.rs` `.php` `.html` | An `otag: +project @context #tag note` comment line within the first ten lines, written in the file's comment style below any shebang, encoding, `<!DOCTYPE>` or `<?php` line |
 
 ### Import and Export
 
@@ -150,4 +150,4 @@ types = [".mp3", ".flac"]
 tags = "genre"
 ```
 
-`plugins` limits which plugins run (`hash//` is listed as `hashdoubleslash`), `types` overrides the file types a plugin handles (`write` ignores types the plugin does not support), and `id3.map` additionally reads an audio tag (here `GENRE`) into a category.
+`plugins` limits which plugins run, `types` overrides the file types a plugin handles (`write` ignores types the plugin does not support), and `id3.map` additionally reads an audio tag (here `GENRE`) into a category.
diff --git a/orvanitag/orvani.py b/orvanitag/orvani.py
index e1fbaa1..03a1df2 100644
--- a/orvanitag/orvani.py
+++ b/orvanitag/orvani.py
@@ -22,7 +22,7 @@ CONTEXTS = {
 
 DEFAULT_PLUGINS = [
     'frontmatter',
-    'hashdoubleslash',
+    'comment',
     'id3',
     'office',
     'pdf'
diff --git a/orvanitag/plugins/comment.py b/orvanitag/plugins/comment.py
new file mode 100644
index 0000000..ceb2f66
--- /dev/null
+++ b/orvanitag/plugins/comment.py
@@ -0,0 +1,103 @@
+"""
+Tags in a source file as a single comment line near the top, like `# otag: +project @context #tag note`.
+"""
+import os
+import re
+import shutil
+
+NAME = 'comment'
+MARKER = 'otag:'
+LINES = 10 # how far from the top the tag line is looked for
+
+HASH = ('# ', '')
+SLASH = ('// ', '')
+DASH = ('-- ', '')
+HTML = ('<!-- ', ' -->')
+STYLES = {
+    '.c' : SLASH,
+    '.cgi' : HASH,
+    '.cpp' : SLASH,
+    '.cs' : SLASH,
+    '.go' : SLASH,
+    '.h' : SLASH,
+    '.hs' : DASH,
+    '.html' : HTML,
+    '.java' : SLASH,
+    '.js' : SLASH,
+    '.kt' : SLASH,
+    '.php' : SLASH,
+    '.pl' : HASH,
+    '.py' : HASH,
+    '.rb' : HASH,
+    '.rs' : SLASH,
+    '.sh' : HASH,
+    '.toml' : HASH,
+    '.ts' : SLASH,
+}
+TYPES = list(STYLES)
+
+# Comment openings a tag line may start with, and the closings it may end with
+OPENINGS = ['#', '//', '--', '<!--', '/*']
+CLOSINGS = ['-->', '*/']
+# Python's encoding declaration only works in the first two lines (PEP 263)
+CODING = re.compile(r'^[ \t\f]*#.*?coding[:=]')
+
+
+def find(lines: list):
+    """Returns the index and the contexts of the tag line, or (None, None)"""
+    for num, line in enumerate(lines[:LINES]):
+        opening, marker, contexts = line.strip().partition(MARKER)
+        if marker and opening.strip() in OPENINGS:
+            for closing in CLOSINGS:
+                contexts = contexts.strip().removesuffix(closing)
+            return num, contexts.strip()
+    return None, None
+
+
+def header(lines: list, suffix: str) -> int:
+    """Returns how many leading lines have to stay above the tag line"""
+    count = 0
+    if lines and (lines[0].startswith('#!') or lines[0].lower().startswith('<!doctype')):
+        count = 1
+    if suffix == '.php':
+        # Outside of the PHP block the comment would be sent as output
+        if not lines or lines[0].strip() != '<?php':
+            raise ValueError('PHP files need `<?php` on a line of its own at the top')
+        count = 1
+    while count < 2 and count < len(lines) and CODING.match(lines[count]):
+        count += 1
+    return count
+
+
+def reader(o):
+    with o.file.open(encoding='utf-8', errors='replace') as data:
+        num, contexts = find([next(data, '') for _ in range(LINES)])
+    if contexts:
+        return o.context(o.string(contexts))
+
+
+def writer(o):
+    with o.file.open(encoding='utf-8', newline='') as data: # keeps \r\n line endings
+        text = data.read()
+    lines = text.splitlines(keepends=True)
+    newline = '\r\n' if '\r\n' in text else '\n'
+    opening, closing = STYLES[o.file.suffix.lower()]
+    line = f'{opening}{MARKER} {" ".join(o.collect(o.context))}{closing}{newline}'
+
+    num, contexts = find(lines)
+    if num is not None:
+        lines[num] = line
+    else:
+        num = header(lines, o.file.suffix.lower())
+        # A blank line keeps the tag from becoming a doc comment, e.g. of a Go package
+        blank = [] if num < len(lines) and not lines[num].strip() else [newline]
+        lines[num:num] = [line] + blank
+
+    tmp = o.file.with_name(f'.{o.file.name}.tmp')
+    try:
+        with open(tmp, 'w', encoding='utf-8', newline='') as data:
+            data.write(''.join(lines))
+        shutil.copymode(o.file, tmp)
+        os.replace(tmp, o.file)
+    finally:
+        tmp.unlink(missing_ok=True)
diff --git a/orvanitag/plugins/hashdoubleslash.py b/orvanitag/plugins/hashdoubleslash.py
deleted file mode 100644
index 28e8130..0000000
--- a/orvanitag/plugins/hashdoubleslash.py
+++ /dev/null
@@ -1,63 +0,0 @@
-import re
-from pathlib import Path
-
-NAME = 'hash//'
-REGEX = r'\s*([@+]\w+|#\w+(?<!#//))'
-PREFIX = '#// '
-MLC_C = ['/*', '*/']
-MLC_Python = ['"""', '"""']
-MLC_Perl = ['=begin', '=end']
-MAP = {
-    '.c' : MLC_C,
-    '.cgi' : MLC_Perl,
-    '.pl' : MLC_Perl,
-    '.class' : MLC_C,
-    '.cpp' : MLC_C,
-    '.cs' : MLC_C,
-    '.go' : MLC_C,
-    '.h' : MLC_C,
-    '.hs' : ['{-', '-}'],
-    '.html' : ['<!--', '-->'],
-    '.java' : MLC_C,
-    '.js' : MLC_C,
-    '.kt' : MLC_C,
-    '.md' : ['---', '---'],
-    '.php' : MLC_C,
-    '.py' : MLC_Python,
-    '.rb' : MLC_Perl,
-    '.rs' : MLC_C,
-    '.ts' : MLC_C,
-    '.txt' : ['---', '---'],
-}
-TYPES = MAP.keys()
-
-def reader(o):
-    with o.file.open() as data:
-        for line_num, line in enumerate(data, start=1):
-            if line_num > 5:
-                break 
-            if line.strip().startswith("#// "):
-                argv = o.string(line.strip()[3:])
-                context = o.context(argv)
-                return context
-            
-def writer(o):
-    string = PREFIX + ' '.join(o.collect(o.context)) + '\n'
-    with o.file.open() as data:
-        content = data.readlines()
-        num = 0
-        line = ''
-        if len(content):
-            for num, line in enumerate(content):
-                if line.strip().startswith("#// ") or num > 3:
-                    break
-        if not num > 3 and line.strip().startswith("#// "):
-            content[num] = string
-            with o.file.open('w') as file:
-                file.writelines(content)
-        else:
-            frontmatter = MAP[o.file.suffix][0] + '\n' + string + MAP[o.file.suffix][1] + '\n'
-            with o.file.open('r+') as file:
-                content = file.read()
-                file.seek(0, 0)
-                file.write(frontmatter + content)
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
index 5abfb94..6829042 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,4 +1,4 @@
-#// +orvanitag @orga #tagging #python
+# otag: +orvanitag @orga #tagging #python
 
 [build-system]
 requires = ["setuptools>=77"]
diff --git a/tests/test_comment.py b/tests/test_comment.py
new file mode 100644
index 0000000..3318a0a
--- /dev/null
+++ b/tests/test_comment.py
@@ -0,0 +1,91 @@
+import os
+import shutil
+import subprocess
+import sys
+
+import pytest
+
+import orvanitag.orvani as orvani
+from orvanitag.orvani import OrvaniTag
+
+
+@pytest.fixture
+def cwd(tmp_path, monkeypatch):
+    monkeypatch.chdir(tmp_path)
+    return tmp_path
+
+
+def write(name, content, *tags):
+    with open(name, 'w', newline='') as file:
+        file.write(content)
+    OrvaniTag().add(name, *tags)
+    return OrvaniTag().write_metadata(name, 'comment')
+
+
+def read_back(cwd, name):
+    (cwd / orvani.CONTEXT_FILE).unlink()
+    OrvaniTag().read_metadata(name)
+    return (cwd / orvani.CONTEXT_FILE).read_text()
+
+
+def test_python_keeps_shebang_coding_and_docstring(cwd):
+    source = '#!/usr/bin/env python3\n# -*- coding: utf-8 -*-\n"""Real docstring."""\nprint(__doc__)\n'
+    (cwd / 's.py').write_text(source)
+    os.chmod(cwd / 's.py', 0o755)
+    assert write('s.py', source, '+tools', '#demo', 'a note')[0] == 0
+    assert (cwd / 's.py').read_text() == (
+        '#!/usr/bin/env python3\n# -*- coding: utf-8 -*-\n# otag: +tools #demo a note\n\n'
+        '"""Real docstring."""\nprint(__doc__)\n'
+    )
+    assert os.stat(cwd / 's.py').st_mode & 0o111
+    run = subprocess.run([sys.executable, 's.py'], capture_output=True, text=True)
+    assert run.stdout == 'Real docstring.\n'
+    assert read_back(cwd, 's.py') == 's.py --- +tools #demo a note\n'
+
+
+@pytest.mark.skipif(not shutil.which('perl'), reason='perl not installed')
+def test_perl_still_runs(cwd):
+    assert write('s.pl', 'print "perl ok\\n";\n', '#demo')[0] == 0
+    run = subprocess.run(['perl', 's.pl'], capture_output=True, text=True)
+    assert run.stdout == 'perl ok\n'
+
+
+def test_php_tag_goes_inside_the_php_block(cwd):
+    assert write('p.php', '<?php\necho "ok";\n', '#demo')[0] == 0
+    assert (cwd / 'p.php').read_text() == '<?php\n// otag: #demo\n\necho "ok";\n'
+
+
+def test_php_without_own_opening_line_is_refused(cwd):
+    with pytest.raises(ValueError):
+        write('p.php', '<?php echo "ok"; ?>\n', '#demo')
+    assert (cwd / 'p.php').read_text() == '<?php echo "ok"; ?>\n'
+
+
+def test_go_tag_is_not_a_package_doc_comment(cwd):
+    assert write('m.go', 'package main\n', '#demo')[0] == 0
+    assert (cwd / 'm.go').read_text() == '// otag: #demo\n\npackage main\n'
+
+
+def test_html_keeps_doctype_first(cwd):
+    assert write('i.html', '<!DOCTYPE html>\n<html></html>\n', '#demo', 'home page')[0] == 0
+    assert (cwd / 'i.html').read_text() == '<!DOCTYPE html>\n<!-- otag: #demo home page -->\n\n<html></html>\n'
+    assert read_back(cwd, 'i.html') == 'i.html --- #demo home page\n'
+
+
+def test_existing_tag_line_is_replaced_and_crlf_kept(cwd):
+    source = '// otag: #old\r\n\r\nint main() {}\r\n'
+    assert write('m.c', source, '#new')[0] == 0
+    assert (cwd / 'm.c').read_bytes() == b'// otag: #new\r\n\r\nint main() {}\r\n'
+
+
+def test_reads_block_comment_and_toml(cwd):
+    (cwd / 'a.js').write_text('/* otag: +site #ui */\nlet a = 1\n')
+    (cwd / 'pyproject.toml').write_text('# otag: +orvanitag @orga\n[project]\n')
+    OrvaniTag().scan('.', False)
+    assert (cwd / orvani.CONTEXT_FILE).read_text() == 'a.js --- +site #ui\npyproject.toml --- +orvanitag @orga\n'
+
+
+def test_marker_inside_code_is_ignored(cwd):
+    (cwd / 'a.py').write_text('x = "otag: #nope"\n')
+    OrvaniTag().scan('.', False)
+    assert not (cwd / orvani.CONTEXT_FILE).exists()