Autolinker.js

Automatic linking of URLs, emails, phone numbers, mentions, and hashtags in text.

Input:  "Visit google.com" 
         
               |
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               v

Output: "Visit <a href="https://google.com">google.com</a>"

Because I had so much trouble finding a good auto-linking implementation out in the wild, I decided to roll my own. It seemed that everything I found was either an implementation that didn't cover every case, had many false positives linked, or was just limited in one way or another.

So, this utility attempts to handle everything. It:

• Autolinks URLs, whether or not they start with the protocol (i.e. 'http://'). In other words, it will automatically link the text "google.com", as well as "http://google.com". Will also autolink IPv4 addresses.
• Will properly handle URLs with query params, anchors, and special characters, and not include chars like a trailing . at the end of a sentence, or a ) char if the URL is inside parenenthesis.
• Will autolink email addresses
• Will autolink phone numbers
• Will autolink mentions (Twitter, Instagram, Soundcloud, TikTok, Youtube)
• Will autolink hashtags (Twitter, Instagram, Facebook, TikTok, Youtube)
• Won't clobber URLs with hash anchors by treating them as hashtags (like some other libraries do). For example: google.com/#anchor is properly linked.
• Will properly handle HTML input. The utility will not overwrite an href attribute inside anchor (<a>) tags (or any other tag/attribute), and will not accidentally wrap the inner text of <a>/<script>/<style> tags with a new one (which cause doubly-nested anchor tags, or mess with scripts)
• Will do all of this in O(n) (linear) time with low constant factors and without the possibility of RegExp Catastrophic Backtracking, making it extremely fast and unsusceptible to pathological inputs.

Quick benchmarks comparison:

(please let me know of other comparable libraries to compare to!)

Hope that this utility helps you as well!

Full API Docs: http://gregjacobs.github.io/Autolinker.js/api/
Live Example: http://gregjacobs.github.io/Autolinker.js/examples/live-example/

Upgrading from a previous major version of Autolinker?

See Breaking Changes at the bottom of this readme.

Installation

Installing with npm:

npm install autolinker --save

Installing with Yarn:

yarn add autolinker

Installing with pnpm:

pnpm add autolinker

Installing with Bower:

bower install Autolinker.js --save

Direct download

Simply clone this repository or download a zip of the project, and link to either dist/Autolinker.js or dist/Autolinker.min.js with a <script> tag.

Importing Autolinker

ES6+/TypeScript/Webpack/Node.js ESM:

import Autolinker from 'autolinker';

Node.js CommonJS:

const Autolinker = require('autolinker');
// note: npm wants an all-lowercase package name, but the utility is a class and
// should be aliased with a capital letter

Browser

<!-- 'Autolinker.js' or 'Autolinker.min.js' - non-minified is better for 
     debugging, minified is better for users' download time -->
<script src="path/to/autolinker/dist/Autolinker.min.js"></script>

Usage

Using the static link() method:

const linkedText = Autolinker.link(textToAutolink[, options]);

Using as a class:

const autolinker = new Autolinker([ options ]);

const linkedText = autolinker.link(textToAutoLink);

Note: if using the same options to autolink multiple pieces of html/text, it's slightly more efficient to create a single Autolinker instance, and run the link() method repeatedly (i.e. use the "class" form above).

Examples:

const linkedText = Autolinker.link("Check out google.com");
// Produces: "Check out <a href="http://google.com" target="_blank" rel="noopener noreferrer">google.com</a>"

const linkedText = Autolinker.link("Check out google.com", { 
    newWindow: false 
});
// Produces: "Check out <a href="http://google.com">google.com</a>"

Options

The following are the options which may be specified for linking. These are specified by providing an Object as the second parameter to Autolinker.link(). These include:

• newWindow : boolean
  true to have the links should open in a new window when clicked, false otherwise. Defaults to true.

• urls : boolean/Object
  true to have URLs auto-linked, false to skip auto-linking of URLs. Defaults to true.

  This option also accepts an Object form with 3 properties to allow for more customization of what exactly gets linked. All default to true:

  • schemeMatches (boolean): true to match URLs found prefixed with a scheme, i.e. http://google.com, or other+scheme://google.com, false to prevent these types of matches.
  • tldMatches: true to match URLs with known top level domains (.com, .net, etc.) that are not prefixed with a scheme (i.e. 'http://'). Ex: google.com, asdf.org/?page=1, etc. Set to false to prevent these types of matches.
  • ipV4Matches (boolean): true to match IPv4 addresses. Ex: 192.168.0.1. false to prevent these types of matches. Note that if the IP address had a prefixed scheme (such as 'http://'), and schemeMatches is true, it will still be linked.

  Example usage: urls: { schemeMatches: true, tldMatches: false, ipV4Matches: true }

• email : boolean
  true to have email addresses auto-linked, false to skip auto-linking of email addresses. Defaults to true.

• phone : boolean
  true to have phone numbers auto-linked, false to skip auto-linking of phone numbers. Defaults to true.

• mention : string
  A string for the service name to have mentions (@username) auto-linked to. Supported values at this time are 'twitter', 'soundcloud', 'instagram', 'tiktok', and 'youtube'. Pass false to skip auto-linking of mentions. Defaults to false.

• hashtag : boolean/string
  A string for the service name to have hashtags auto-linked to. Supported values at this time are 'twitter', 'facebook', 'instagram', 'tiktok', and 'youtube'. Pass false to skip auto-linking of hashtags. Defaults to false.

• stripPrefix : boolean
  true to have the 'http://' (or 'https://') and/or the 'www.' stripped from the beginning of displayed links, false otherwise. Defaults to true.

  This option also accepts an Object form with 2 properties to allow for more customization of what exactly is prevented from being displayed. Both default to true:

  • scheme (boolean): true to prevent the scheme part of a URL match from being displayed to the user. Example: 'http://google.com' will be displayed as 'google.com'. false to not strip the scheme. NOTE: Only an 'http://' or 'https://' scheme will be removed, so as not to remove a potentially dangerous scheme (such as 'file://' or 'javascript:').
  • www (boolean): true to prevent the 'www.' part of a URL match from being displayed to the user. Ex: 'www.google.com' will be displayed as 'google.com'. false to not strip the 'www'.

• stripTrailingSlash : boolean
  true to remove the trailing slash from URL matches, false to keep the trailing slash. Example when true: http://google.com/ will be displayed as http://google.com. Defaults to true.

• truncate : number/Object
  A number for how many characters long URLs/emails/Twitter handles/Twitter hashtags should be truncated to inside the text of a link. If the match is over the number of characters, it will be truncated to this length by replacing the end of the string with a two period ellipsis ('..').

  Example: a url like 'http://www.yahoo.com/some/long/path/to/a/file' truncated to 25 characters may look like this: 'yahoo.com/some/long/pat..'

  In the object form, both length and location may be specified to perform truncation. Available options for location are: 'end' (default), 'middle', or 'smart'. Example usage:

  truncate: { length: 32, location: 'middle' }
  

  The 'smart' truncation option is for URLs where the algorithm attempts to strip out unnecessary parts of the URL (such as the 'www.', then URL scheme, hash, etc.) before trying to find a good point to insert the ellipsis if it is still too long. For details, see source code of: TruncateSmart

• className : string
  A CSS class name to add to the generated anchor tags. This class will be added to all links, as well as this class plus "url"/"email"/"phone"/"hashtag"/"mention" suffixes for styling url/email/phone/hashtag/mention links differently.

  The name of the hashtag/mention service is also added as a CSS class for those types of matches.

  For example, if this config is provided as "my-link", then:

  • URL links will have the CSS classes: "my-link my-link-url"
  • Email links will have the CSS classes: "my-link my-link-email"
  • Phone links will have the CSS classes: "my-link my-link-phone"
  • Twitter mention links will have the CSS classes: "my-link my-link-mention my-link-twitter"
  • Instagram mention links will have the CSS classes: "my-link my-link-mention my-link-instagram"
  • Hashtag links will have the CSS classes: "my-link my-link-hashtag my-link-twitter"

• decodePercentEncoding: boolean
  true to decode percent-encoded characters in URL matches, false to keep the percent-encoded characters.

  Example when true: https://en.wikipedia.org/wiki/San_Jos%C3%A9 will be displayed as https://en.wikipedia.org/wiki/San_José.

  Defaults to true.

• replaceFn : Function
  A function to use to programmatically make replacements of matches in the input string, one at a time. See the section Custom Replacement Function for more details.

• sanitizeHtml : boolean
  

  true to HTML-encode the start and end brackets of existing HTML tags found in the input string. This will escape < and > characters to < and >, respectively.

  Setting this to true will prevent XSS (Cross-site Scripting) attacks, but will remove the significance of existing HTML tags in the input string. If you would like to maintain the significance of existing HTML tags while also making the output HTML string safe, leave this option as false and use a tool like https://github.com/cure53/DOMPurify (or others) on the input string before running Autolinker.

  Defaults to false.

For example, if you wanted to disable links from opening in new windows, you could do:

const linkedText = Autolinker.link("Check out google.com", { 
    newWindow: false 
});
// Produces: "Check out <a href="http://google.com">google.com</a>"

And if you wanted to truncate the length of URLs (while also not opening in a new window), you could do:

const linkedText = Autolinker.link("http://www.yahoo.com/some/long/path/to/a/file", { 
    truncate: 25, 
    newWindow: false 
});
// Produces: "<a href="http://www.yahoo.com/some/long/path/to/a/file">yahoo.com/some/long/pat..</a>"

More Examples

One could update an entire DOM element that has unlinked text to auto-link them as such:

const myTextEl = document.getElementById('text');
myTextEl.innerHTML = Autolinker.link(myTextEl.innerHTML);

Using the same pre-configured Autolinker instance in multiple locations of a codebase (usually by dependency injection):

const autolinker = new Autolinker({ newWindow: false, truncate: 25 });

//...

autolinker.link("Check out http://www.yahoo.com/some/long/path/to/a/file");
// Produces: "Check out <a href="http://www.yahoo.com/some/long/path/to/a/file">yahoo.com/some/long/pat..</a>"

//...

autolinker.link( "Go to www.google.com" );
// Produces: "Go to <a href="http://www.google.com">google.com</a>"

Retrieving the List of Matches

If you're just interested in retrieving the list of Matches without producing a transformed string, you can use the parse() method.

For example:

const matches = Autolinker.parse("Hello google.com, I am asdf@asdf.com", {
    urls: true,
    email: true
});

console.log(matches.length);         // 2
console.log(matches[0].type);        // 'url'
console.log(matches[0].getUrl());    // 'google.com'
console.log(matches[1].type);        // 'email'
console.log(matches[1].getEmail());  // 'asdf@asdf.com'

Custom Replacement Function

A custom replacement function (replaceFn) may be provided to replace url/email/phone/mention/hashtag matches on an individual basis, based on the return from this function.

Full example, for purposes of documenting the API:

const input = "...";  // string with URLs, Email Addresses, Mentions (Twitter, Instagram), and Hashtags

const linkedText = Autolinker.link(input, {
    replaceFn : function(match) {
        console.log("href = ", match.getAnchorHref());
        console.log("text = ", match.getAnchorText());

        switch(match.type) {
            case 'url':
                console.log("url: ", match.getUrl());

                return true;  // let Autolinker perform its normal anchor tag replacement

            case 'email':
                const email = match.getEmail();
                console.log("email: ", email);

                if(email === "my@own.address") {
                    return false;  // don't auto-link this particular email address; leave as-is
                } else {
                    return;  // no return value will have Autolinker perform its normal anchor tag replacement (same as returning `true`)
                }

            case 'phone':
                console.log("Phone Number: ", match.getPhoneNumber());

                return '<a href="http://newplace.to.link.phone.numbers.to/">' + match.getPhoneNumber() + '</a>';

            case 'mention':
                console.log("Mention: ", match.getMention());
                console.log("Mention Service Name: ", match.getServiceName());

                return '<a href="http://newplace.to.link.mention.handles.to/">' + match.getMention() + '</a>';

            case 'hashtag':
                console.log("Hashtag: ", match.getHashtag());

                return '<a href="http://newplace.to.link.hashtag.handles.to/">' + match.getHashtag() + '</a>';
        }
    }
} );

Modifying the default generated anchor tag

const input = "...";  // string with URLs, Email Addresses, Mentions (Twitter, Instagram), and Hashtags

const linkedText = Autolinker.link( input, {
    replaceFn : function( match ) {
        console.log("href = ", match.getAnchorHref());
        console.log("text = ", match.getAnchorText());

        const tag = match.buildTag();       // returns an `Autolinker.HtmlTag` instance for an <a> tag
        tag.setAttr('rel', 'nofollow');   // adds a 'rel' attribute
        tag.addClass('external-link');    // adds a CSS class
        tag.setInnerHtml('Click here!');  // sets the inner html for the anchor tag

        return tag;
    }
} );

The replaceFn is provided one argument:

1. An Autolinker.match.Match object which details the match that is to be replaced.

A replacement of the match is made based on the return value of the function. The following return values may be provided:

1. No return value (undefined), or true (boolean): Delegate back to Autolinker to replace the match as it normally would.
2. false (boolean): Do not replace the current match at all - leave as-is.
3. Any string: If a string is returned from the function, the string will be used directly as the replacement HTML for the match.
4. An Autolinker.HtmlTag instance, which can be used to build/modify an HTML tag before writing out its HTML text.

Full API Docs

The full API docs for Autolinker may be referenced at: http://gregjacobs.github.io/Autolinker.js/api/

Live Example

http://gregjacobs.github.io/Autolinker.js/examples/

Upgrading from v3.x -> v4.x (Breaking Changes)

1. Internet Explorer support has been removed since its official demise in June 2022.
2. The urls.wwwMatches config has been removed. A www. prefix is now treated like any other subdomain of a top level domain (TLD) match (such as 'subdomain.google.com').
3. Match.getType() should be replaced with Match.type. This allows for TypeScript type narrowing of Match objects returned by the parse() method or inside the replaceFn.
4. The Matcher classes have been removed in favor of a single finite state machine parser, greatly improving the performance of Autolinker (3x performance improvement over the 3.x branch), but removing some of the customizability of the old regular expressions. Will address this customizability in a future release.
5. Autolinker.AnchorTagBuilder, Autolinker.HtmlTag, and Autolinker.match.* references have been removed. These shouldn't be needed as public APIs, but please raise a GitHub issue if these are for some reason needed.

Upgrading from v2.x -> v3.x (Breaking Changes)

1. If you are still on v1.x, first follow the instructions in the Upgrading from v1.x -> v2.x section below.
2. The HtmlParser class has been removed in favor of an internal parseHtml() function which replaces the old regexp-based implementation with a state machine parser that is guaranteed to run in linear time. If you were using the HtmlParser class directly, I recommend switching to htmlparser2, which implements the HTML semantics better. The internal parseHtml() function that Autolinker now uses is fairly geared towards Autolinker's purposes, and may not be useful in a general HTML parsing sense.

Upgrading from v1.x -> v2.x (Breaking Changes)

1. If you are still on v0.x, first follow the instructions in the Upgrading from v0.x -> v1.x section below.

2. The codebase has been converted to TypeScript, and uses ES6 exports. You can now use the import statement to pull in the Autolinker class and related entities such as Match:

   // ES6/TypeScript/Webpack
   import Autolinker, { Match } from 'autolinker';
   

   The require() interface is still supported as well for Node.js:

   // Node.js
   const Autolinker = require('autolinker');
   

3. You will no longer need the @types/autolinker package as this package now exports its own types

4. You will no longer be able to override the regular expressions in the Matcher classes by assigning to the prototype (for instance, something like PhoneMatcher.prototype.regex = ...). This is due to how TypeScript creates properties for class instances in the constructor rather than on prototypes.

   The idea of providing your own regular expression for these classes is a brittle notion anyway, as the Matcher classes rely on capturing groups in the RegExp being in the right place, or even multiple capturing groups for the same piece of information to support a different format. These capturing groups and associated code are subject to change as the regular expression needs to be updated, and will not involve a major version release of Autolinker.

   In the future you will be able to override the default Matcher classes entirely to provide your own implementation, but please raise an issue (or +1 an issue) if you think the library should support a currently-unsupported format.

Upgrading from v0.x -> v1.x (Breaking Changes)

1. twitter option removed, replaced with mention (which accepts 'twitter', 'instagram' and 'soundcloud' values)
2. Matching mentions (previously the twitter option) now defaults to being turned off. Previously, Twitter handle matching was on by default.
3. replaceFn option now called with just one argument: the Match object (previously was called with two arguments: autolinker and match)
4. (Used inside the replaceFn) TwitterMatch replaced with MentionMatch, and MentionMatch.getType() now returns 'mention' instead of 'twitter'
5. (Used inside the replaceFn) TwitterMatch.getTwitterHandle() -> MentionMatch.getMention()

Developing / Contributing

Pull requests definitely welcome. To setup the project, make sure you have Node.js installed. Then open up a command prompt and type the following:

npm install -g pnpm@latest   # this project uses pnpm workspaces, and pnpm is a faster npm anyway :)

cd Autolinker.js             # where you cloned the project
pnpm install

To run the tests:

pnpm run test

• Make sure to add tests to check your new functionality/bugfix
• Run the pnpm run test command to test

Running the Live Example Page Locally

Run:

pnpm run devserver

Then open your browser to: http://localhost:8080/docs/examples/index.html

You should be able to make a change to source files, and refresh the page to see the changes.

Running the benchmarks

Run:

pnpm run benchmarks

Note: See the Benchmarks Table above for current results.

Couple points on the benchmarks:

• These benchmarks attempt to set up all libraries by configuring comparable features to Autolinker (e.g.: linking emails, hashtags, mentions, etc.) to try to get an apples-to-apples comparison.
• While developing, recommend running the benchmarks a few times both before and after making any changes if developing.
• See the benchmarks folder and benchmarks/input-text.ts for how the benchmarks are set up and what input they are given.

Documentation Generator Notes

This project uses JSDuck for its documentation generation, which produces the page at http://gregjacobs.github.io/Autolinker.js.

Unfortunately, JSDuck is a very old project that is no longer maintained. As such, it doesn't support TypeScript or anything from ES6 (the class keyword, arrow functions, etc). However, I have yet to find a better documentation generator that creates such a useful API site. (Suggestions for a new one are welcome though - please raise an issue.)

Since ES6 is not supported, we must generate the documentation from the ES5 output. As such, a few precautions must be taken care of to make sure the documentation comes out right:

1. @cfg documentation tags must exist above a class property that has a default value, or else it won't end up in the ES5 output. For example:

   // Will correctly end up in the ES5 output
   
   /**
    * @cfg {String} title
    */
   readonly title: string = '';
   
   
   
   // Will *not* end up in ES5 output, and thus, won't end up in the generated
   // documentation
   
   /**
    * @cfg {String} title
    */
   readonly title: string;
   

2. The @constructor tag must be replaced with @method constructor

To build the documentation, you will need Ruby installed (note: Ruby comes pre-installed on MacOS), with the JSDuck gem.

See https://github.com/senchalabs/jsduck#getting-it for installation instructions on Windows/Mac/Linux.

Changelog

See Releases