Text fragments
Text fragments allow linking directly to a specific portion of text in a web document, without requiring the author to annotate it with an ID, using particular syntax in the URL fragment. Supporting browsers are free to choose how to draw attention to the linked text, e.g., with a color highlight and/or scrolling to the content on the page. This is useful because it allows web content authors to deep-link to other content they don't control, without relying on the presence of IDs to make that possible. Building on top of that, it could be used to generate more effective content-sharing links for users to pass to one another.
Concepts and usage
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:
- 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:
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:
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.
Syntax
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.
textEndOptional-
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.
-suffixOptional-
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.
Usage notes
-
Text strings used for the
textStart,textEnd,prefix-, and-suffixvalues need to be percent-encoded. In addition, the standard requires the URL-safe dash character'-'to be similarly percent-encoded. -
Matches are case-insensitive.
-
Individual
textStart,textEnd,prefix-, and-suffixstrings need to reside wholly inside the same block-level element, but complete matches can span across multiple element boundaries. -
For security reasons, when linking to a cross-origin page using this feature, you should open the link in a
noopenercontext — you need to addrel="noopener"to yourelements, and addnoopenerto yourwindow.open()calls when using this feature. -
Text fragments are invoked only on user-initiated navigations.
-
Text fragments are only applied to the main frame; text will not be searched inside