Have you ever visited a website from your mobile phone to find the number of a business you wanted to call and tried to copy that link?  Wouldn't it be easier if their phone number were click-to-call?  Or if they offered you a button to click while on your phone?

Much like clicking on an email address often opens your email system with a subject already created, many other communication systems can be click to call.

At times, just making text a link is enough.  However, consider also giving your visitors a button to click. Here's how to format the html for each type, a dummy link, and the same link applied to an image.

Click-To-Call Link HTML Formatting

<a href="tel:[PHONE-NUMBER]">[PHONE-NUMBER]</a>

callto:[phone_number]
mainly appropriate for iPhone and Nokia phones
wtai://wp/mc;[phone_number]
mainly appropriate for Android phones
tel:[phone_number]
reported to work on most of the newest devices. If you want to have only one type of URI, use this one.

In the phone number you can use +(plus) sign for international numbers. What's also interesting to know is that this can even work on a desktop if you have an application like Skype installed. So maybe it's a good idea to have this on the classic/desktop website too.

Later update from comments. Another interesting phone link will be how to call a teleconferencing phone number. There you call a phone number and then you enter your conference code, usually followed by hash(#). To do this from a link you will need a pause after the phone number and this is done with , (comma), usually entered by a long press on star(*). I tested this on Android and iOS and it works fine, but you usually need two pauses (,) between the phone number and conference code. Same way you can dial an extension line.
Examples

callto: 02836028937
call 02836028937 on iPhone and Nokia
wtai://wp/mc;02836028937
call 12345678 on Android
wtai://wp/mc;+842836028937
call an international number on Android
tel:02836028937
call 02836028937 on most of the newer devices
tel:02836028937,,100200#
join 100200 conference code on the conference line 02836028937 on most of the newer devices
tel:+842836028937,,100200#
join 100200 conference code on the international conference line +842836028937on most of the newer devices.

Click-To-SMS Link HTML Formatting

<a href="sms:[PHONE-NUMBER]?body=[MESSAGE]">[PHONE-NUMBER]</a>

SMS

From a web page you can open the SMS sending application on the user phone with a link like below:

    sms:<phone_number>[,<phone-number>]*[?body=<message_body>]

The link contains a comma separated list of phone numbers and an optional message body. The phone numbers are specified as in the call links. Detailed information you can find in the URI Scheme for GSM Short Message Service (draft)
Examples

sms:0084836028937
SMS to 0084836028937
sms:0084836028937?body=Hello my friend
SMS "Hello my friend" to 0084836028937
sms:0084836028937,+0084836028937?body=Hello
SMS to multiple phone numbers, including an international one

There is also an URI version for MMS starting with mms:. On some (mobile) browsers (devices) it is also reported to work smsto: and mmsto:, although I would recommend the first version.

iPhone/iPod/iTunes

When developing a website iPhone is definitely to be considered. You can include links to items in the iTunes store, such as movies, music or application. Apple provided for your convenience a web interface to create such links: ITMS Link Maker. Just specify the country, the search keyowrds and what type of iTunes items. You will get a list of items and when you click one you will get the link. You can even get the link for an author. These links will both work on the desktop and iPhone.

Example: Fluid application (free)

Android market

Android is gaining market share as we speak. Nexus One was just released and in my opinion will beat iPhone. As you include links to iTunes, you can include links to applications in Android Market.

    market://search?q=<query>

The query can include keywords or can identify a specific application using q=pname:your.package.name and then the link will be market://search?q=pname:dvms.cungvui.

Ovi Store

Nokia created a new fresh application repository for their latest phone – Ovi Store. If you want to include a link to an application, search for it and then copy the link that it will look like http://store.ovi.com/content/XXXXX?clickSource=publisher+channel. Just remove the last part and include http://store.ovi.com/content/21309 into your page, where XXXXX is the application Id. You can also include a link to a publisher's page containing a summary of their application. The link is found on any of the publisher's application (see by Publisher Name) and it will look like http://store.ovi.com/publisher/Publisher+Name
Windows Marketplace

We cannot exclude Microsoft from the list with their Windows Phone Marketplace. Same steps to find out the application link: search it, copy the link location and strip the last part. The link will look like http://marketplace.windowsphone.com/details.aspx?appId=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, where xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx is the application ID, clearly resembling a GUID. Here publishers don't have a personal page.
BlackBerry App World

For all those BlackBerry fans, there is BlackBerry App World. Again same process: search for the application and copy the link location of the application icon. The format is http://appworld.blackberry.com/webstore/content/XXXXX, where XXXXX is the application ID. The app authors have a page here with a summary of their apps. See the by Author link under each application. The link will be like http://appworld.blackberry.com/webstore/vendor/XXXX, where XXXX is the author ID.

Geolocation

Nowadays you cannot even imagine a world without maps and GPS. More and more contact pages include a map too. Nowadays smart phones usually include a map application and opening a map with your location in it would be quite nice for the user

    geopoint:latitude,longitude

As simple as this and you know where to go.

Messengers

From a web site you can also interact with the messenger applications installed on your machine.
Yahoo Messenger

    ymsgr:ACTION?USERNAME&m=YOUR+MESSAGE

The possible actions are addfriend, sendIM and call. The message can, of course, be specified only for sendIM action. The USERNAME should be your.account@yahoo.com or your.account@hotmail.com.

Example: ymsgr:sendIM?dvms&m=Hello – Say Hello in Yahoo Messenger.

Windows Messenger

    msnim:ACTION?contact=USERNAME

The possible actions are chat, add (to add a contact), voice (for voice call) and video (for video call). The USERNAME should be your.account@yahoo.com or your.account@hotmail.com.

Example: msnim:chat?contact=dvms@yahoo.com – Chat with me in Windows Messenger.

Google Talk

    gtalk:ACTION?jid=USERNAME&from_jid=YOURNAME

The possible actions are chat and call (for voice call). The USERNAME and YOURNAME should be your.account@gmail.com. The parameter from_jid is optional and it should be specified only if you use multiple accounts.

Example: gtalk:chat?jid=dvms@yahoo.com – Chat with me in Google Talk.

Skype

    skype:USERNAME?ACTION

The possible actions are chat, add (to add a contact), userinfo (to view a profile) and voicemail (to leave a voicemail). The USERNAME is your Skype ID.

Example: skype:chat?jid=dvms– Chat with me in Skype.

Lync

Updated on 03/15/2015

    sip:USERNAME@DOMAIN>

The main thing here is the sip protocol. It is possible that this protocol can be used by other applications too, not being something specific to Lync.

Example: Call John.

There is also AIM, IRC and some others but we will not get into any other details for the moment.

Mail

It's pretty easy to include a link for sending an email into your webpage. Basically it's replacing the http scheme with mailto. So the link will look something like:

    mailto:<email>[,<email>]*[?<arguments>]

Such a link will practically open the system application for sending emails (like Outlook or Thunderbird) and the message will be prepopulated with some values. As you can notice you can use multiple email addresses (To) separated by comma.

The possible arguments to be included are:

subject
    the message Subject field
cc
    the message CC field as a comma separated list of addresses
bcc
    the message BCC field as a comma separated list of addresses
body
    the message body. If you include a new line in your message you should include %0A.

Examples

mailto:sale@dvms.vn
    the simplest mailto link
mailto:sale@dvms.vn,info@dvms.vn
    multiple email addresses
"mailto:sale@dvms.vn?subject=Testing mailto
    specify a subject
"mailto:sale@dvms.vn?subject=Testing mailto&cc=info@dvms.vn
    specify a subject and CC

Just as a side note in the end, it's better not to rely on this kind of mechanism for handling email on your website. A contact form that sends an email could be a better idea.

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