If you use meta robots tags on your pages, you can give search engines instructions on how you’d like them to crawl or index parts of your website. This page lists an overview of all the different values you can have in the meta robots tag, what they do, and which search engines support each value.

The different robots meta tag values

The following values (‘parameters’) can be placed on their own, or together in the content attribute of tag (separated by a comma), to control how search engines interact with your page.

Scroll down for an overview of which search engines support which specific parameters.

Allow search engines to add the page to their index, so that it can be discovered by people searching.
Note: When there are no directives relating to indexing, this is assumed to be the default.
Disallow search engines from adding this page to their index, and therefore disallow them from showing it in their results.
Note: Informal messaging from Google suggests that, if a page is set to noindex for a long period of time, it may also be treated as if it were also set to nofollow. The precise mechanics of this are unclear, and it’s unclear whether other search engines behave similarly.
Tells the search engines that it may follow links on the page, to discover other pages.
Note: When there are no directives relating to following links, this is assumed to be the default.
Tells the search engines robots to ‘endorse’ (pass equity through) any links on the page.
Note: It’s unclear (and inconsistent between search engines) whether this attribute prevents search engines from following links, or just prevents them from assigning any value to those links.
A shortcut for noindex, nofollow.
A shortcut for index, follow.
Note: This is assumed by default on all pages, and does nothing if specified.
Disallow search engines from indexing images on the page.
Note: If images are linked to directly from elsewhere, search engines can still index them, so using an X-Robots-Tag HTTP header is generally a better idea.
Prevents the search engines from showing a cached copy of this page in their search results listings.
Same as noarchive, but only used by MSN/Live.
Prevents the search engines from showing a text or video snippet (i.e., a meta description) of this page in the search results, and prevents them from showing a cached copy of this page in their search results listings.
Note: Snippets may still show an image thumbnail, unless noimageindex is also used.
Prevents the search engine from showing an inline search box for your site.
Prevents the search engine from reading your page’s content aloud via voice services/results.
Prevents search engines from showing translations of the page in their search results.
Sets a maximum number of characters for the meta description.
Note: Omitting this tag may result in an implied value of 0. A default value of -1 should be set to imply ‘no limit’.
Sets a maximum number of seconds for a video in a preview.
Note: Omitting this tag may result in an implied value of 0. A default value of -1 should be set to imply ‘no limit’.
Sets a maximum image size for use in a preview (none, standard or large).
Note: Omitting this tag may result in an implied value of none.
Indicates that a page contains adult material.
Tells search engines a date/time after which they should not show it in search results; a ‘timed’ version of noindex.
Note: Must be in RFC850 format (e.g., Monday, 15-Aug-05 15:52:01 UTC).
Prevents the search results snippet from using the page description from the Yandex Directory.
Note: Only supported by Yandex.
Blocks Yahoo from using the description for this page in the Yahoo directory as the snippet for your page in the search results.
Note: Since Yahoo closed its directory this tag is deprecated, but you might come across it once in awhile.

Which search engine supports which robots meta tag values?

This table shows which search engines support which values. Note that the documentation provided by some search engines is sparse, so there are many unknowns.

Robots value Google Yahoo Bing Ask Baidu Yandex
Indexing controls
index Y* Y* Y* ? Y Y
noindex Y Y Y ? Y Y
noimageindex Y N N ? N N
Whether links should be followed
follow Y* Y* Y* ? Y Y
nofollow Y Y Y ? Y Y
none Y ? ? ? N Y
all Y ? ? ? N Y
Snippet/preview controls
noarchive Y Y Y ? Y Y
nocache N N Y ? N N
nosnippet Y N Y ? N N
nositelinkssearchbox Y N N N N N
nopagereadaloud Y N N N N N
notranslate Y N N ? N N
max-snippet:[number] Y Y N N N N
max-video-preview:[number] Y Y N N N N
max-image-preview:[setting] Y Y N N N N
rating Y N N N N N
unavailable_after Y N N ? N N
noodp N Y** Y** ? N N
noydir N Y** N ? N N
noyaca N N N N N Y

* Most search engines have no specific documentation for this, but we’re assuming that support for excluding parameters (e.g., nofollow) implies support for the positive equivalent (e.g., follow).
** Whilst the noodp and noydir attributes may still be ‘supported’, these directories no longer exist, and it’s likely that these values do nothing.

Rules for specific search engines

Sometimes, you might want to provide specific instructions to a specific search engine, but not to others. Or you may want to provide completely different instructions to different search engines.

In these cases, you can change the value of the content attribute to a specific search engine (e.g., googlebot).

Note: Given that search engines will simply ignore instructions which they don’t support or understand, it’s very rare to need to use multiple meta robots tags to set instructions for specific crawlers.

Conflicting parameters, and robots.txt files

It’s important to remember that meta robots tags work differently to instructions in your robots.txt file, and that conflicting rules may cause unexpected behaviors. For example, search engines won’t be able to see your meta tags if the page is blocked via robots.txt.

You should also take care to avoid setting conflicting values in your meta robots tag (such as using both index and noindex parameters) – particularly if you’re setting different rules for different search engines. In cases of conflict, the most restrictive interpretation is usually chosen (i.e., “don’t show” usually beats “show”).

Adding a noindex or nofollow to a post or page is a breeze if you’re on WordPress. Read how to use Yoast SEO to keep a post out of the search results.

Resources from the search engines

The post The ultimate guide to the meta robots tag appeared first on Yoast.


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