There are a lot of resources around that show how to do this, but I couldn’t find a comprehensive go-to link, so here we are.

You can create a SharePoint site using the REST API.  Here’s a fully baked example:

<!--
    SiteRequestForm.html: Collect information and create a site for the user.
-->

<צענטער>
<טיש>
    <טר>
        <טד>Site Name:</טד>
        <טד><אַרייַנשרייַב טיפּ="text" נאָמען="SiteName" שייַן="SiteName" /></טד>
    </טר>
    <טר>
        <טד colspan="2">
            <אַרייַנשרייַב טיפּ="submit" שייַן="CreateSiteButton" ווערט="Create the Site" />
        </טד>
    </טר>
</טיש>
</צענטער>

<שריפט סרק="../Plugins/jquery-1.11.0.min.js"></שריפט>

<שריפט>
איז געווען CreateSiteLogicContainer = {

    createSiteData: {
            "parameters": {
                __metadata: { "type": "SP.WebInfoCreationInformation" },
                URL: "Paultest1",
                טיטל: "Paultest1",
                באַשרייַבונג: "rest-created web by Paul!",
                שפּראַך: 1033,
                WebTemplate: "sts",
                UseUniquePermissions: פאַלש
            }
    },

    createSite: פונקציע () {

        jQuery.support.cors = ריכטיק;

        CreateSiteLogicContainer.createSiteData.parameters.Url = $("#SiteName").וואַל();
        
        $.ajax({
            URL: "https://bigapplesharepoint.sharepoint.com/NBAIADev/_api/web/webinfos/add",
            מעטאָד: "POST",

            headers: {
                "Accept": "application/json; odata=verbose",
                "content-type": "application/json;odata=verbose",
                "X-RequestDigest": $("#__REQUESTDIGEST").וואַל()
            },

            דאַטע: JSON.stringify(CreateSiteLogicContainer.createSiteData),

            success: פונקציע () { פלינק("success"); },
            גרייַז: פונקציע () { פלינק("error"); }

        });
    },

    wireUpForm: פונקציע () {
        $("#CreateSiteButton").גיט(פונקציע () {
            פלינק("About to try and create the site.");
            CreateSiteLogicContainer.createSite();
        });
    }


}

CreateSiteLogicContainer.wireUpForm();

</שריפט>

When successful, you get a JSON packet in response like this:

My key thoughts and learnings from this include:

• This approach uses jQuery.  אין מיין פאַל, my jQuery library is located in “../plugins.”  You’ll want to change that to point to your favorite JQ location.
• You can copy and paste that whole snippet into a Content Editor Web Part on a page and it should work just fine.  You’ll want to change the end point of the API call and make sure you reference JQ correctly.
• The URL is relative to your API’s endpoint.  אין מיין פאַל, it’s creating sub-sites underneath https://bigapplesharepoint.com
• You don’t need to provide a content-length. Some blog posts and MSDN document implies that you do, but happened for me automatically, which I assume is being handled by the $.ajax call itself.
• This line is required in order to avoid a “forbidden” response: "X-RequestDigest": $("#__REQUESTDIGEST").וואַל().  There are other ways to do it, but this is pretty nice.  I have lost the link to blog that provided this shortcut.  H/T to you, mysterious blogger!

Good luck and hope this helps someone out.

</עק>

אַבאָנירן צו מיין בלאָג.

גיי מיר אויף טוויטטער בייַ http://www.twitter.com/pagalvin