Text fragments

Historically, one of the web's key features has always been its ability to provide links between different documents — it is what makes the web, a web:

• You can link to the top of a document by linking to its URL, for example:
  • https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a.
• You can link to a specific section of a document by linking to its URL plus the document fragment (ID) of that section, for example:
  • https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#browser_compatibility.

The issue with linking to specific document fragments is that the author of the linked page needs to put an anchor in place to actually link to. The second example above links to an h2 element with an ID of browser_compatibility:

<h2 id="browser_compatibility">
  <a href="#browser_compatibility">Browser compatibility</a>
</h2>

If the ID is changed or removed, the document fragment is ignored, and the link just links through to the top of the page. This is reasonable in terms of graceful degradation, but it would arguably be better if the author of the link had full control over where they link to, without needing to rely on the page author.

Text fragments make this a reality — they allow link authors to specify text content to link to, rather than document fragments, in a flexible manner.

In a similar manner to document fragments, text fragments are appended onto a URL after a hash symbol (#). The syntax however is a bit different:

https://example.com#:~:text=[prefix-,]textStart[,textEnd][,-suffix]

The key parts to understand are as follows:

:~:

Otherwise known as the fragment directive, this sequence of characters tells the browser that what comes next is one or more user-agent instructions, which are stripped from the URL during loading so that author scripts cannot directly interact with them. User-agent instructions are also called directives.

text=

A text directive. This provides a text fragment to the browser, defining what text is to be linked to in the linked document.

textStart

A text string specifying the start of the linked text.

textEnd Optional

A text string specifying the end of the linked text.

prefix- Optional

A text string followed by a hyphen specifying what text should immediately precede the linked text, only allowing for whitespace in between. This helps the browser to select the correct linked text, in cases where there are multiple matches.

-suffix Optional

A hyphen followed by a text string specifying what text should immediately follow the linked text, only allowing for whitespace in between. This helps the browser to select the correct linked text, in cases where there are multiple matches.

Supporting browsers will scroll to and highlight the first text fragment in the linked document that matches the specified directive. Note that it is possible to specify multiple text fragments to highlight in the same URL by separating them with ampersand (&) characters.

• Text strings used for the textStart, textEnd, prefix-, and -suffix values need to be percent-encoded.

• Matches are case-insensitive.

• Individual textStart, textEnd, prefix-, and -suffix strings need to reside wholly inside the same block-level element, but complete matches can span across multiple element boundaries.

• For security reasons, the feature requires links to be opened in a noopener context — you need to add rel="noopener" to your <a> elements, and add noopener to your window.open() calls when using this feature.

• Text fragments are invoked only on full (non-same-page), user-initiated navigations.

• Text fragments are only applied to the main frame; text will not be searched inside <iframe>s, and iframe navigation will not invoke a text fragment.

• For sites that wish to opt-out, Chromium-based browsers support a Document Policy header value that they can send so user agents will not process Text Fragments:

  http

  Document-Policy: force-load-at-top
  

• https://example.com#:~:text=for scrolls to and highlights the first instance of the text for in the document.
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=human scrolls to and highlights the first instance of the text human in the document.
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=linked%20URL scrolls to and highlights the first instance of the text linked URL in the document.

• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=human,URL scrolls to and highlights the first instance of a text string starting with human and ending with URL.
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=linked%20URL,defining%20a%20value scrolls to and highlights the first instance of a text string starting with linked URL and ending with defining a value. Note how the highlighted text spans across multiple block-level elements.

• https://example.com#:~:text=asking-,for scrolls to and highlights the second instance of the text for in the document.
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=sent-,referrer scrolls to and highlights the first instance of the text referrer that has the text sent directly before it. This is the 5th instance of referrer in the document; without the prefix, the first instance would be highlighted.
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=linked%20URL,-'s%20format scrolls to and highlights the first instance of the text linked URL that has the text 's format directly following it. This is the 5th instance of linked URL in the document; without the suffix, the first instance would be highlighted.
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=downgrade:-,The%20Referer,be%20sent,-to%20origins scrolls to and highlights the instance of the text The Referer ... be sent that is prefixed by downgrade: and suffixed by to origins. This illustrates a more complex example where the prefix/suffix are used to home in on the specific text instance you want to link to. Try removing the prefix, for example, and seeing what is matched.

You can specify multiple text fragments to highlight in the same URL by separating them with ampersand (&) characters. Let's look at a couple of examples:

• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=Causes&text=linked scrolls to and highlights the first instances of the text strings Causes and linked.
• https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#:~:text=linked%20URL,-'s%20format&text=Deprecated-,attributes,attribute scrolls to and highlights two text instances:
  • The first instance of the text linked URL that has the text 's format directly following it.
  • The first instance of a text string starting with attributes and ending with attribute, which is prefixed by Deprecated.

If you don't see one or more of your text fragments highlighted and you are sure you've got the syntax correct, you might just be highlighting a different instance than the one you expected. It might be highlighted, but offscreen.

Browsers are free to style the highlighted text in whatever default way they choose. The CSS Pseudo-Elements Module Level 4 defines a pseudo-element, ::target-text, which allows you to specifying custom styling.

For example, in our scroll-to-text demo we have the following CSS:

::target-text {
  background-color: rebeccapurple;
  color: white;
}

Try following the above link in a supporting browser to see the effect this has.

The FragmentDirective object, which is accessed via the Document.fragmentDirective property, can be used to test whether or not text fragments are supported in a browser.

Try running the following in a supporting browser's devtools, in a tab with one or more matched text fragments:

document.fragmentDirective;
// returns an empty FragmentDirective object, if supported
// undefined otherwise

This functionality is mainly intended for feature detection at present. In the future, the FragmentDirective object could include additional information.

FragmentDirective

An object representing the text fragments. Currently empty and mainly intended for feature detection.

Document.fragmentDirective

Returns the FragmentDirective for the current document.

::target-text

Represents the highlighted text fragments in the current document. It allows authors to customize the styling of text fragments.

• Boldly link where no one has linked before: Text Fragments