Explicitly opting-in has the advantage of receiving useful changes or targeted posts a bot might otherwise skip by following "opt-out" behavior by default. Users should be aware that by opting-out of bot posts, they will not be notified of matters relating to material they have edited or uploaded, which are tagged or scanned by bots per policy.

In particular, in the encyclopedia spaces:

• Avoid using the template as a blunt instrument
• Address the root problem with the bot owner or bot community
• Remove the template tag once the underlying problem has been resolved.

Most bots will NOT understand these templates when they are indirectly transcluded.

Most bots will not disregard the template if it is inside of <nowiki>...</nowiki> tags. For example, if you are discussing the templates with another editor, please use the {{tl}} template, e.g. {{tl|nobots}}, which will show {{nobots}}, rather than <nowiki>{{nobots}}</nowiki>, which will possibly be parsed as intending to exclude bots from the page.

A list of transclusions is at User:AnomieBOT/Nobots Hall of Shame

{{nobots}}                Ban all compliant bots (shortcut that takes no parameters)
{{bots}}                  Allow all bots (shortcut that takes no parameters)

{{bots|allow=<botlist>}}  Ban all compliant bots not in the list
{{bots|deny=<botlist>}}   Ban all compliant bots in the list

Where <botlist> is a comma-delimited string of bot usernames (AWB can be used for all AWB-based bots):
  {{bots|allow=SineBot,Legobot}}
  {{bots|deny=AWB}}

<botlist> can also be "none" or "all" as in the following examples:
  {{bots|allow=all}}      Allow all bots
  {{bots|allow=none}}     Ban all compliant bots

  {{bots|deny=all}}       Ban all compliant bots
  {{bots|deny=none}}      Allow all bots

Bots are not bound to observe the nobots template; it will depend on their functionality, their owners and their terms of approval. The bots that currently support exclusion are listed at exclusion compliant bots.

Another option is to opt out of specific types of messages for users who wish to be notified of certain problems, but not others. Users should be aware that by opting-out of specific notification posts, they will not be notified of matters relating to material they have edited or uploaded, which are tagged per policy. Actions (such as deletion) may be executed without you being notified as a result. By applying this to your own user talk page, you agree to this consequence. Applying this to a user talk page other than your own will be considered vandalism. All bots and scripts that leave messages on a user's talk page are encouraged to add this capability.

By adding this to a user's talk page, a user may still receive these messages by non-compliant bots or scripts, or humans who add the tag manually.

{{bots|optout=all}}            Opt out of all messages (see limitations below).

{{bots|optout=nosource}}       Opt out of no source messages.
{{bots|optout=nolicense}}      Opt out of no license messages.
{{bots|optout=orfud}}          Opt out of orphaned fair use messages.
{{bots|optout=npd}}            Opt out of no permission messages.
{{bots|optout=norationale}}    Opt out of no rationale messages.
{{bots|optout=replaceable}}    Opt out of replaceable fair use messages.
{{bots|optout=bettersource}}   Opt out of better source request messages.
{{bots|optout=afd}}            Opt out of articles for deletion messages or variant forms.
{{bots|optout=ifd}}            Opt out of images for deletion messages or variant.
{{bots|optout=prod}}           Opt out of prod warning.
{{bots|optout=MassMessage}}    Opt out of Mass messages.

Items can be combined by putting a comma between options

{{bots|optout=nosource,nolicense}}                 Opt out of no source, and no license messages.
{{bots|optout=orfud,norationale,replaceable}}      Opt out of fair use messages.

Some message notifications are not allowed to be opted out. These include:

1. Copyright violation notifications
2. Vandalism (and other) warning notices.
3. User:SineBot's notices for not signing posts
4. Any message tag that isn't included as a way of opting out above. (Is there one that should be included? Leave a message on the talk page.)
5. Mass messages cannot be opted-out of by using {{bots|optout=all}}; users must explicitly opt out with {{bots|optout=MassMessage}}

These syntaxes look correct, but depending on the individual bot may not have the intended effect.

• Pywikibot supports bots and nobots since r4096. The templates may be ignored using a parameter.
• Since version 3.2.0.0 AutoWikiBrowser fully supports {{bots}} and {{nobots}}. Additionally, pseudo-username AWB can be specified to ban all AWB-based bots from the page. However, AWB has an option to ignore these templates.
• Opt out message notification was introduced here April 3, 2008. Individual bot/script implementation will vary and notice above of implementation may not include this feature.

function allowBots( $text, $user ) {
    if (preg_match('/\{\{(nobots|bots\|allow=none|bots\|deny=all|bots\|optout=all|bots\|deny=.*?'.preg_quote($user,'/').'.*?)}}/iS',$text))
        return false;
    if (preg_match('/\{\{(bots\|allow=all|bots\|allow=.*?'.preg_quote($user,'/').'.*?)}}/iS', $text))
        return true;
    if (preg_match('/\{\{(bots\|allow=.*?)}}/iS', $text))
        return false;
    return true;
}

sub allow_bots {
    my($text, $user, $opt) = @_;
    return 0 if $text =~ /{{[nN]obots}}/;
    return 1 if $text =~ /{{[bB]ots}}/;
    if($text =~ /\{\{[bB]ots\s*\|\s*allow\s*=\s*(.*?)\s*}}/s){
        return 1 if $1 eq 'all';
        return 0 if $1 eq 'none';
        my @bots = split(/\s*,\s*/, $1);
        return (grep $_ eq $user, @bots) ? 1 : 0;
    }
    if($text =~ /\{\{[bB]ots\s*\|\s*deny\s*=\s*(.*?)\s*}}/s){
        return 0 if $1 eq 'all';
        return 1 if $1 eq 'none';
        my @bots = split(/\s*,\s*/, $1);
        return (grep $_ eq $user, @bots) ? 0 : 1;
    }
    if(defined($opt) && $text =~ /\{\{[bB]ots\s*\|\s*optout\s*=\s*(.*?)\s*}}/s){
        return 0 if $1 eq 'all';
        my @opt = split(/\s*,\s*/, $1);
        return (grep $_ eq $opt, @opt) ? 0 : 1;
    }
    return 1;
}

Public Shared Function AllowBots(ByVal text As String, ByVal user As String) As Boolean
    Return Not Regex.IsMatch(text, "\{\{(nobots|bots\|(allow=none|deny=(?!none).*(" & user.Normalize() & "|all)|optout=all))\}\}", RegexOptions.IgnoreCase)
End Function

public static bool AllowBots(string text, string user)
{
    return !Regex.IsMatch(text, @"\{\{(nobots|bots\|(allow=none|deny=(?!none).*(" + user.Normalize() + @".*|all)|optout=all))\}\}", RegexOptions.IgnoreCase);
}

public static boolean allowBots(String text, String user)
{
      return !text.matches("(?si).*\\{\\{(nobots|bots\\|(allow=none|deny=([^\\}]*?" + user + "[^\\}]*?|all)|optout=all))\\}\\}.*");
}

function allowBots(text, user){
  if (!new RegExp("\\{\\{\\s*(nobots|bots[^}]*)\\s*\\}\\}", "i").test(text)) return true;
  return (new RegExp("\\{\\{\\s*bots\\s*\\|\\s*deny\\s*=\\s*([^}]*,\\s*)*" + user.replace(/([\(\)\*\+\?\.\-\:\!\=\/\^\$])/g, "\\$1") + "\\s*(?=[,\\}])[^}]*\\s*\\}\\}", "i").test(text)) ? false : new RegExp("\\{\\{\\s*((?!nobots)|bots(\\s*\\|\\s*allow\\s*=\\s*((?!none)|([^}]*,\\s*)*" + user.replace(/([\(\)\*\+\?\.\-\:\!\=\/\^\$])/g, "\\$1") + "\\s*(?=[,\\}])[^}]*|all))?|bots\\s*\\|\\s*deny\\s*=\\s*(?!all)[^}]*|bots\\s*\\|\\s*optout=(?!all)[^}]*)\\s*\\}\\}", "i").test(text);
}

This code assumes that the mwparserfromhell library was installed and imported in the current script.

def allow_bots(text, user):
	user = user.lower().strip()
	text = mwparserfromhell.parse(text)
	for tl in text.filter_templates():
		if tl.name.matches(['bots', 'nobots']):
			break
	else:
		return True
	for param in tl.params:
		bots = [x.lower().strip() for x in param.value.split(",")]
		if param.name == 'allow':
			if ''.join(bots) == 'none': return False
			for bot in bots:
				if bot in (user, 'all'):
					return True
		elif param.name == 'deny':
			if ''.join(bots) == 'none': return True
			for bot in bots:
				if bot in (user, 'all'):
					return False
	if (tl.name.matches('nobots') and len(tl.params) == 0):
		return False
	return True

• Template:Bots at Meta-Wiki
• User:AnomieBOT/nobots tests - An index of pages for testing the handling of bot exclusion templates.