Add comments and replies

Comments are user-provided feedback on a file, such as a reader of a word processing document suggesting how to rephrase a sentence. There are two types of comments: anchored comments and unanchored comments. An anchored comment is associated with a specific location, such as a sentence in a word processing document, within a specific version of a document. Conversely, an unanchored comment is just associated with the document.

Replies are attached to comments and represent a user's response to the comment. The Drive API enables you to allow your users to add comments and replies to documents created by your app. Collectively, a comment with replies is known as a discussion.

For a full synopsis of the Drive API's commenting API, watch the following video:

Add an unanchored comment

To add an unanchored comment to a document, call comments.create with the fileId and a comments resource containing the comment.

The comment is inserted as plain text, but the response body provides an htmlContent field containing content formatted for display.

Important: We recommend you check that a user has the correct permissions to add comments. Further, only the creator of a comment or reply can delete or edit a comment or reply. Errors occur when a user in a non-creator role tries to delete or edit a comment. To avoid these errors, check the author.me field of the comments resource to ensure the user making the request is the author of the comment and then verify their permissions relative to the comment.

Add a reply to a comment

To add a reply to a comment, call replies.create with the comment, fileId, and a reply resource containing the reply.

The reply is inserted as plain text, but the response body provides an htmlContent field containing content formatted for display.

Add an anchored comment to the latest revision of a document

When you add a comment, you might want to anchor it to a region in the file. An anchor defines the file revision and region in a file to which a comment refers. The Comments resource defines the anchor field as a JSON string.

Important: Anchors are immutable, and their position relative to the content of a document cannot be guaranteed between revisions. We recommend that you use anchors in documents where the position does not change, for example in image files or read-only documents.

To add an anchored comment:

1. (Optional). Call revisions.list to list all of the revisionIDs for a document. Only follow this step if you want to anchor a comment to any revision other than the latest revision. If you want to use the latest revision, use head for the revisionID.

2. Call comments.create with the fileID, a comments resource containing the comment, and a JSON anchor string containing the revisionID (r) and region (a).

How you define a region depends on the type of document content you are working with. For further information, refer to Define a region.

Note: We recommend you check that a user has the correct permissions to add comments. Further, only the creator of a comment or reply can delete or edit a comment or reply. Errors occur when a person in a non-creator role tries to delete or edit a comment. To avoid these errors, check the author.me field of the comments resource.

Define a region

As mentioned earlier, the JSON anchor string contains a revisionID (r) and region (a). The region (a) is a JSON array containing region classifiers specifying the format and location to which a comment is anchored. A classifier might be a as a two-dimensional rectangle for an image, a line of text in a document, a time duration in a video, and so on. To define a region, select the region classifier that matches the type of content you are trying to anchor to. For example, if your content is text, you are likely going to use either txt or line region classifier.

For a list of region classifiers provided in the Google Drive API, refer to Google Drive API region classifiers.

The following example shows a JSON anchor string that anchors comments to lines in two separate areas of a document:

• The first area starts at line 12 ('n':12) and extends for 3 lines ('l':3).
• The second area only covers line 18 ('n':12, 'l':`).

    {
      'r': revisionId,
      'a': [
      {
        'line':
        {
          'n': 12,
          'l': 3,
        }
      },
      {
        'line':
        {
          'n': 18,
          'l': 1,
        }
      }]
    }

Important: If your app lets users update and share multiple revisions of a document, comments on older revisions may no longer apply to the anchored location. Therefore, you must indicate to which revision each comment belongs clearly in your UI.

Google Drive API region classifiers

Following is a list of all of the region classifiers included with the Drive API:

rect

A rectangle in a two dimensional image.

Property	Description	Type
x	Position on the x axis, units default to pixels for images and percent for PDFs.	Double
y	Position on the y axis, units default to pixels for images and percent for PDFs.	Double
w	Length on the x axis, units default to pixels for images and percent for PDFs.	Double
h	Length on the y axis, units default to pixels for images and percent for PDFs.	Double
mw	The full width of the document at the time when the comment was made. Use this to make x and w unitless since they can act like a percentage.	Double
mh	The height width of the document at the time when the comment was made. See mw above for purpose.	Double
r	The degrees of rotation of the document. E.g. if an image is rotated 90 degrees clockwise then a rectangle at 0,0 displays in the top right of the image. Should be one of 0, 90, 180, 270	Double

page

A page number in a pdf or tiff or other document with pages. Use this for documents with page-like elements (e.g. spreadsheets, slide, and layer).

Property	Description	Type
p	The page number (0-indexed).	Integer
mp	The number of pages in this document.	Integer

time

A duration of time in a video or other document with a time dimension | Integer

Property	Description	Type
t	The start time.	hh:MM:ss.frac formatted time string (where M = minutes, m = millis, hours and minutes are optional)
d	The duration of the time range.	hh:MM:ss:mmm formatted time string (where M = minutes, m = millis)
md	The full time duration of the document.	hh:MM:ss:mmm formatted time string (where M = minutes, m = millis)

txt

A range of text

Property	Description	Type
o	Start offset (character offset from the start of the file).	Integer
l	The length of the text range.	Integer
ml	The length of this document in characters.	Integer

line

A specific line in a text file or any files with lines in it.

Property	Description	Type
n	Line number.	Integer
l	The length of the line range.	Integer
ml	The maximum number of lines in the file.	Integer

matrix

A location in a matrix-like structure. Use to define row and columns in spreadsheet documents, or any other documents which have a row or column structure.

Property	Description	Type
c	The column number.	Integer
r	The row number.	Integer
w	The number of columns.	Integer
h	The number of rows.	Integer
mw	The Maximum width.	Integer
mh	The Maximum height.	Integer

Resolve a comment

Use the comment.update method to set the resolved property in the comments resource to true when a comment has been addressed.

When your app sets the resolved property to true, your UI should indicate that the comment has been addressed. For example, your app might:

• disallow further replies and greying out all previous replies and the original comment.
• hide resolved comments.

Delete a comment

Use the comments.delete method to delete comments. When a comment is deleted, Google Drive marks the comment resource as "deleted": "true".

List comments

Use the comments.list method to list comments. If you want to include deleted comments in the results, set the includedDeleted field to true.