# Developer's Guide: Protocol **Important**: This is an old version of this page. For the latest version, use the links in the left-side navbar. The Blogger Data API allows client applications to view and update Blogger content in the form of Google Data API feeds. Your client application can use the Blogger Data API to create new blog posts, edit or delete existing blog posts, and query for blog posts that match particular criteria. In addition to providing some background on the capabilities of the Blogger Data API, this document provides examples of basic Data API interactions using raw XML and HTTP. After reading this document, you may want to learn more about interacting with the API using our [client libraries](https://developers.google.com/gdata/docs/client-libraries) by reading the programming-language-specific sections of this developer's guide. ## Contents 1. [Audience](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#Audience) 2. [Getting started](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#GettingStarted) 1. [Creating a Blogger account](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#CreatingAccount) 3. [Authenticating to the Blogger service](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#Authenticating) 1. [AuthSub proxy authentication](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#AuthSub) 2. [ClientLogin username/password authentication](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#ClientLogin) 4. [Retrieving a list of blogs](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#RetrievingMetafeed) 5. [Creating posts](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#CreatingEntries) 1. [Publishing a blog post](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#CreatingPublicEntries) 2. [Creating a draft blog post](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#CreatingDraftEntries) 6. [Retrieving posts](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#RetrievingEntries) 1. [Retrieving all blog posts](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#RetrievingWithoutQuery) 2. [Retrieving posts using query parameters](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#RetrievingWithQuery) 7. [Updating posts](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#UpdatingEntries) 8. [Deleting posts](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#DeletingEntries) 9. [Comments](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#Comments) 1. [Creating comments](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#CreatingComments) 2. [Retrieving comments](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#RetrievingComments) 3. [Deleting comments](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#DeletingComments) 10. [Export format](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#ExportFormat) ## Audience This document is intended for programmers who want to write client applications that can interact with Blogger using XML and HTTP. This document assumes that you understand the general ideas behind the [Google Data APIs protocol](https://developers.google.com/gdata/docs/2.0/basics). If you're using a UNIX system and you want to try the examples in this document without writing any code, you may find the UNIX command-line utilities `curl` or `wget` useful; for more information, see the manual pages for those utilities. For Blogger Data API reference information, see the [Protocol reference guide](https://developers.google.com/blogger/docs/1.0/reference). ## Getting started ### Creating a Blogger account You may want to [sign up for a Blogger account](http://www.blogger.com/signup.g) for testing purposes. Blogger uses [Google Accounts](https://www.google.com/accounts/Login), so if you already have a Google account, you're all set. ## Authenticating to the Blogger service You can access both public and private feeds using the Blogger Data API. Public feeds don't require any authentication, but they are read-only. If you want to modify blogs, then your client needs to authenticate before requesting private feeds. It can authenticate using either of two approaches: [AuthSub](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#AuthSub) proxy authentication or [ClientLogin](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#ClientLogin) username/password authentication. For more information about authentication with Google Data APIs in general, see the [authentication documentation](https://developers.google.com/gdata/docs/auth/overview). Most of the samples in subsequent sections of this document assume you're supplying the appropriate authentication. ### AuthSub proxy authentication AuthSub proxy authentication is used by web applications that need to authenticate their users to Google Accounts. The website operator and the client code don't have access to the username and password for the Blogger user; instead, the client obtains special AuthSub tokens that allow the client to act on a particular user's behalf. For more detailed information, see the [AuthSub documentation](https://developers.google.com/accounts/docs/AuthSub). When a user first visits your application, they have not yet been authenticated. In this case, you need to display some information and a link directing the user to a Google page to authenticate your request for access to their blogs. The following query parameters are included in the AuthSubRequest URL: next : The URL of the page that Google should redirect the user to after authentication. scope : Indicates that the application is requesting a token to access Blogger feeds. The scope string to use is `http://www.blogger.com/feeds/` (URL-encoded, of course). secure : Indicates whether the client is requesting a secure token. session : Indicates whether the token returned can be exchanged for a multi-use (session) token. The AuthSubRequest URL might look like this: ``` https://www.google.com/accounts/AuthSubRequest?scope=http%3A%2F%2Fwww.blogger.com%2Ffeeds%2F&session=1&secure=0&next=http%3A%2F%2Fwww.example.com%2Fwelcome.html ``` The user follows the link to Google's site and authenticates to their Google Account. After the user authenticates, the AuthSub system redirects them to the URL you specified in the `next` query parameter of the AuthSubRequest URL. The AuthSub system appends an authentication token to that URL, as the value of the `token` query parameter. For example: ``` http://www.example.com/welcome.html?token=yourAuthToken ``` This token value represents a single-use AuthSub token. In this example, since `session=1` was specified, this token can be exchanged for an AuthSub session token by calling the [`AuthSubSessionToken`](https://developers.google.com/accounts/docs/AuthSub#AuthSubSessionToken) service with the single-use token in an Authorization header, as follows: ``` GET /accounts/AuthSubSessionToken HTTP/1.1 Content-Type: application/x-www-form-urlencoded Authorization: AuthSub token="yourAuthToken" User-Agent: Java/1.5.0_06 Host: www.google.com Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2 Connection: keep-alive ``` The AuthSubSessionToken service response includes a `Token` header that contains the session token and an `Expiration` header that indicates how long the token will remain valid. Your application can then use the session token value in the `Authorization` header of subsequent interactions with Blogger. Here's an example of an HTTP request, containing a non-secure token, that you might send to Blogger: ``` GET /feeds/blogID/blogs/posts/defaults HTTP/1.1 Content-Type: application/x-www-form-urlencoded Authorization: AuthSub token="yourSessionToken" User-Agent: Java/1.5.0_06 Host: www.blogger.com Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2 Connection: keep-alive ``` ### ClientLogin username/password authentication Use ClientLogin authentication if your client is a standalone, single-user "installed" client (such as a desktop application). To request an authentication token using the ClientLogin mechanism, send a `POST` request to the following URL: ``` https://www.google.com/accounts/ClientLogin ``` The `POST` body should contain a set of query parameters that look like parameters passed by an HTML form, using the `application/x-www-form-urlencoded` content type. These parameters are: Email : The user's email address. Passwd : The user's password. service : The Blogger service name is `blogger`. (For other service names, see the [service name list](https://developers.google.com/gdata/faq#clientlogin).) accountType : This should always be set to `GOOGLE` when using the Blogger API. Failure to set this parameter will prevent access by users who also have a [G Suite](http://www.google.com/a/) account. source : Identifies your client application. Should take the form companyName-applicationName-versionID. The examples use the name `exampleCo-exampleApp-1`. For more information about the parameters, see the [Authentication for Installed Applications](https://developers.google.com/accounts/docs/AuthForInstalledApps#Request) document. If the authentication request fails, then the server returns an HTTP `403 Forbidden` status code. If it succeeds, then the server returns an HTTP `200 OK` status code, plus three long alphanumeric codes in the body of the response: SID, LSID, and Auth. The Auth value is the authorization token that you'll send to Blogger with each of your subsequent requests, so keep a copy of that value. You can ignore the SID and LSID values. Since all requests to private feeds require authentication, you have to set the Authorization header in all subsequent interactions with Blogger, using the following format: ``` Authorization: GoogleLogin auth=yourAuthToken ``` Where `yourAuthToken` is the Auth string returned by the ClientLogin request. For more information about ClientLogin authentication, including sample requests and responses, see the [Authentication for Installed Applications](https://developers.google.com/accounts/docs/AuthForInstalledApps) documentation. **Note**: Use the same token for all requests in a given session; don't acquire a new token for each Blogger request. **Note** : As described in the ClientLogin documentation, the authentication request may fail and request a CAPTCHA challenge. If you want Google to issue and handle the CAPTCHA challenge, then send the user to `https://www.google.com/accounts/DisplayUnlockCaptcha?service=blogger` (rather than to the CAPTCHA-handling URL given in the ClientLogin documentation). ## Retrieving a list of blogs The Blogger Data API provides a feed that lists the blogs for a particular user; that feed is known as a "metafeed." Send an HTTP `GET` to the following URL to retrieve the list of blogs: ``` http://www.blogger.com/feeds/userID/blogs ``` **Note** : You can also substitute `default` for the user ID, which tells Blogger to return the list of blogs for the user whose credentials accompany the request. An entry in the metafeed might look like this: ``` tag:blogger.com,1999:blog-blogID.post-postID 2006-08-02T18:44:43.089-07:00 2006-11-08T18:10:23.020-08:00 Lizzy's Diary Being the journal of Elizabeth Bennet Elizabeth Bennet noreply@blogger.com http://www.blogger.com/profile/profileID ``` For information about what each of those elements means, see the [Google Data APIs Protocol Reference](https://developers.google.com/gdata/docs/2.0/reference#DocumentFormat) document or the [Atom 1.0 specification](http://www.atomenabled.org/developers/syndication/atom-format-spec.php). If your request fails for some reason, Blogger may return a different status code. More information about HTTP status codes is also available in the [Google Data APIs Protocol Reference](https://developers.google.com/gdata/docs/2.0/reference) document. ## Creating posts The Blogger Data API allows you to create and publish new blog entries, as well as creating drafts of entries. ### Publishing a blog post After authenticating, you can publish new blog entries. First, create an XML representation of the post to publish. This XML needs to be in the form of an Atom `` element, which might look like this: ``` Marriage!

Mr. Darcy has proposed marriage to me!

He is the last man on earth I would ever desire to marry.

Whatever shall I do?

 ``` **Note**: Setting a custom author for posts is currently not supported. All new posts will appear as if they were created by the currently authenticated user. To publish this entry, send it to the blog's post URL as follows. First, place your Atom `` element in the body of a new `POST` request, using the `application/atom+xml` content type. Then find the blog's post URL in the metafeed by locating the `` element where the `rel` attribute ends with `#post`. The blog's post URL is given as the `href` attribute of this element, which is in this format: ``` http://www.blogger.com/feeds/blogID/posts/default ``` **Note** : This URL is the same as the URL in the `` tag that appears in the `` section of the human-readable version of the blog. Blogger creates a blog post using the entry you sent, then returns an HTTP `201 CREATED` status code, along with a copy of the new post in the form of an `` element. The entry returned is the same one you sent, but it also contains various elements added by Blogger, such as an `` element. If your request fails for some reason, Blogger may return a different status code. For information about the status codes, see the [Google Data API protocol reference document](https://developers.google.com/gdata/docs/2.0/reference). ### Creating a draft blog post Draft posts are created in the same way as public posts, but with an `` element added to the entry indicating that the post shouldn't (yet) be published. This `` element should contain a single `` element as a child: ``` yes ``` The data contained in the `` element must be the string yes in order for the post to be recognized as a draft. You can turn an existing draft blog post into a published post by retrieving the draft post, setting the `` element's data to the string no, and then updating the post. Retrieving and updating posts is covered in the next two sections. **Note** : For more information on the Atom Publishing Protocol, including the `` and `` namespaces, see [RFC 5023](http://tools.ietf.org/html/rfc5023). ## Retrieving posts The following sections describe how to retrieve a list of blog posts, with and without query parameters. You can query a Blogger public feed without authentication. Therefore, you don't need to set the Authorization parameter when you retrieve blog posts from a public blog. ### Retrieving all blog posts To retrieve the user's posts, send an HTTP `GET` request to the blog's feed URL. Blogger then returns a feed containing the appropriate blog entries. For example, to get a list of blog posts for liz@gmail.com, send the following HTTP request to Blogger (with the appropriate value in place of `blogID`, of course): ``` GET http://www.blogger.com/feeds/blogID/posts/default ``` Blogger then returns an HTTP `200 OK` status code and a standard Atom 1.0 feed containing the blog posts. The following is an example of a feed for a blog with only one post. Notice that we've slightly edited this example to make it a little more readable by humans. In particular, a real Blogger feed contains actual IDs and URLs. ``` tag:blogger.com,1999:blog-blogID 2006-11-08T18:10:23.020-08:00 Lizzy's Diary Elizabeth Bennet noreply@blogger.com http://www.blogger.com/profile/profileID Blogger tag:blogger.com,1999:blog-blogID.post-postID 2006-11-08T18:10:00.000-08:00 2006-11-08T18:10:14.954-08:00 Quite disagreeable <p>I met Mr. Bingley's friend Mr. Darcy this evening. I found him quite disagreeable.</p> Elizabeth Bennet noreply@blogger.com http://www.blogger.com/profile/profileID ``` ### Retrieving posts using query parameters The Blogger Data API lets you request a set of entries that match specified criteria, such as requesting blog posts published or updated in a given date range. For example, to send a date-range query, add the `published-min` and `published-max` parameters to the request URL. To get all the blog entries created between March 16, 2008 to March 24, 2008, send an HTTP request to the blog's feed URL: ``` GET http://www.blogger.com/feeds/blogID/posts/default?published-min=2008-03-16T00:00:00&published-max=2008-03-24T23:59:59 ``` When you send that `GET` request, Blogger returns an HTTP `200 OK` status code and a feed containing any blog posts that were created in the date range you specified. The `updated-min` and `updated-max` parameters may also be used to get all the blog entries updated within a given range. However, note that these parameters are ignored unless the `orderby` parameter is also set to `updated`. The Blogger Data API supports the following query parameters: alt : The type of feed to return, such as `atom` (the default) or `rss`. /category : Specifies categories (also known as labels) to filter the feed results. For example, `http://www.blogger.com/feeds/blogID/posts/default/-/Fritz/Laurie` returns entries with both the labels `Fritz` and `Laurie`. max-results : The maximum number of entries to return. orderby : The order in which to return entries, such as `lastmodified` (the default), `starttime`, or `updated`. published-min, published-max : The bounds on entry publication dates. start-index : The 1-based index of the first result to be retrieved (for paging). updated-min, updated-max : The bounds on entry update dates. These query parameters are ignored unless the `orderby` parameter is set to `updated`. For more information about query parameters, see the [Blogger Data API Reference Guide](https://developers.google.com/blogger/docs/1.0/reference#Parameters) and the [Google Data APIs Reference Guide](https://developers.google.com/gdata/docs/2.0/reference#Queries). ## Updating posts To update an existing blog post, first you retrieve the entry you want to update, then you modify it, and then you send a `PUT` request, with the updated entry in the message body, to the post's edit URL. Be sure that the `` value in the entry you `PUT` exactly matches the `` of the existing entry. The edit URL is highlighted in the following entry: ``` tag:blogger.com,1999:blog-blogID.post-postID 2006-11-08T18:10:00.000-08:00 2006-11-08T18:10:14.954-08:00 Quite disagreeable <p>I met Mr. Bingley's friend Mr. Darcy this evening. I found him quite disagreeable.</p> Elizabeth Bennet noreply@blogger.com http://www.blogger.com/profile/profileID ``` **IMPORTANT** : To ensure forward compatibility, be sure that when you `PUT` an updated entry, you preserve *all* the XML that was present when you retrieved the entry from Blogger. Otherwise, when we implement new stuff and include `` elements in the feed, your client won't return them and your users will miss out. The [Google Data API client libraries](https://developers.google.com/gdata/docs/client-libraries) all handle this correctly, so if you're using one of the libraries you're all set. **Note**: Modifying the author data associated with posts is currently not supported. **Troubleshooting Tip** : Some firewalls block HTTP `PUT` messages. To get around this, you can include a `X-HTTP-Method-Override: PUT` header in a `POST` request. For details, see the [Google Data API protocol basics](https://developers.google.com/gdata/docs/2.0/basics) document. ## Deleting posts To delete a post, send a `DELETE` request to the post's edit URL. This is the same URL used to [update posts](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#UpdatingEntries). **Troubleshooting Tip** : Some firewalls block HTTP `DELETE` messages. To get around this, you can include a `X-HTTP-Method-Override: DELETE` header in a `POST` request. For details, see the [Google Data API protocol basics](https://developers.google.com/gdata/docs/2.0/basics) document. ## Comments The Blogger Data API allows for creating, retrieving, and deleting comments. Updating comments is not supported (nor is it available in the web interface). ### Creating comments To post a comment, create an Atom `` element like the following: ``` This is my first comment This is my first comment ``` To publish this comment, place your Atom `` element in the body of a new `POST` request, using the `application/atom+xml` content type. Then send the `POST` request to the appropriate Blogger URL: ``` POST http://www.blogger.com/feeds/blogID/postID/comments/default ``` **Note**: Currently, you can only post comments to a blog owned by the authenticated user. **Note**: Setting a custom author for comments is currently not supported. All new comments will appear as if they were created by the currently authenticated user. ### Retrieving comments You can retrieve the comments for a particular post by sending a `GET` to this post's comments feed URL: ``` GET http://www.blogger.com/feeds/blogID/postID/comments/default ``` Or you can get the comments from all posts by using the blog's comments feed URL: ``` GET http://www.blogger.com/feeds/blogID/comments/default ``` These requests return a comments feed that looks like this: ``` tag:blogger.com,1999:blog-blogID.post-postID.comment-commentID 2007-04-04T21:56:29.803-07:00 My Blog : Time to relax Blog Author name Blogger 1 1 tag:blogger.com,1999:blog-blogID.post-commentID 2007-04-04T21:56:00.000-07:00 2007-04-04T21:56:29.803-07:00 This is my first comment This is my first comment Blog Author name blog_author@gmail.com http://www.blogger.com/profile/userID ``` ### Deleting comments To delete a comment, send a `DELETE` request to the comment's edit URL. This URL is highlighted in the comments feed above. ## Export format Blogger allows users to export and import their blogs using a Blogger export file. This export file contains all of the posts and comments for one blog. The format for the export file is the exact same Atom format that is described in the sections on retrieving posts and comments. This export file will contain the contents of the post feed and the contents of the comments feed combined into one document. To export or import blog data using the export format, you can visit the **Settings** page for the blog. To retrieve the export file for a blog using the Data API, use the following URL: ``` GET http://www.blogger.com/feeds/blogID/archive ``` To import the export file, create a `POST` request to the following URL with the contents of the export file as the request data and `application/atom+xml` as the content type: ``` POST http://www.blogger.com/feeds/blogID/archive/full ``` Neither of the URLs for above support query parameters. Both requests must also contain [](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#Authenticating)authentication information and only blog administrators will be able to import/export the blog using these feed URLs. **Note**: If you are creating your own Blogger export file, there is currently one restriction around the ordering of the post and comment entries. The Blogger export file will list all of the posts first, and then all of the comments. Interleaving post and comment entries is allowed so long as the comment entry comes after the post the comment is for. For more information about how Blogger uses the Atom format in the export file, see the [Protocol reference guide](https://developers.google.com/blogger/docs/1.0/reference#LinkCommentsToPosts). [Back to top](https://developers.google.com/blogger/docs/1.0/developers_guide_protocol#top)