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How do I comment a block of lines in YAML?

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11 Answers 11

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2634

YAML supports inline comments, but does not support block comments.

From Wikipedia:

Comments begin with the number sign ( # ), can start anywhere on a line, and continue until the end of the line

A comparison with JSON, also from Wikipedia:

The syntax differences are subtle and seldom arise in practice: JSON allows extended charactersets like UTF-32, YAML requires a space after separators like comma, equals, and colon while JSON does not, and some non-standard implementations of JSON extend the grammar to include Javascript's /* ... */ comments. Handling such edge cases may require light pre-processing of the JSON before parsing as in-line YAML.

# If you want to write # a block-commented Haiku # you'll need three pound signs
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5 Comments

So in VSCode you can highlight the lines you want to comment then Ctrl+: and all lines will be comment. You can uncomment with the same way. if the shortcut does not work you can pass by Edit Menu
I think you means to say CTRL+/ for comment not :
The CTRL + / (or CMD + / for mac) works for intellij too
I just spent 5 minutes troubleshooting this, so for any other users with German keyboard layout: For you it is Strg+#
The command is called Toggle Line Comment (@command:editor.action.commentLine) in VS Code and you can bind an arbitrary shortcut to it.
375

The specification only describes one way of marking comments:

An explicit comment is marked by a “#” indicator.

That's all. There aren't any block comments.

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Comments

252

I am not trying to be smart about it, but if you use Sublime Text or Visual Studio Code for your editor, the steps are:

  1. Select the block
  2. Cmd + / on Mac or Ctrl + / on Linux and Windows
  3. Profit

I'd imagine that other editors have similar functionality too. Which one are you using? I'd be happy to do some digging.

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15 Comments

If you're in Eclipse with the YEdit plugin, the standard Eclipse block-comment-toggler of ctrl-/ will toggle block comments in yaml files.
Works in intellij as well.
Works in JetBrains IDEs: RubyMine and Gogland
Works in VSCode too.
This answers a different question than asked. This question asks about the YAML grammar, not about implementation/user details based on a particular tool. (Note: the StackOverflow UX workflow is somewhat constraining, but this is by design. It is designed to promote direct answers to the asked question, not dozens of different answers discussing unnecessary particulars.)
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In Vim you can do one of the following:

  • Comment all lines: :%s/^/#
  • Comment lines 10 - 15: :10,15s/^/#
  • Comment line 10 to current line: :10,.s/^/#
  • Comment line 10 to end: :10,$s/^/#

or using visual block:

  1. Select a multiple-line column after entering visual block via Ctrl+v.
  2. Press r followed by # to comment out the multiple-line block replacing the selection, or Shift+i#Esc to insert comment characters before the selection.
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7 Comments

least amount of thinking possible ;). "Vim, I did a thing. do it here, and here and here and here and here..."
You can also hit : and type s/^/# to comment current selection.
@Conrad.Dean try to learn to think in macros. Though virtually the same for this task, qqI#<esc>jq then @Q@Q@Q@Q@Q@Q (because it's faster to not let off the shift key), is a habit you can extend to much more complex tasks. Start small. Practice often. Soon you will create very complex macros perfectly first try. If you clear the register first qqq, you can include @q before the last q to get recursion (but only to the end of the file).
@BrunoBronosky: instead of all those @q, you can simply do 6@q or 10000@q if you like.
@bodo you can indeed. Most vim commands accept :h count multipliers. But for me, visually anything over 6 and I have to do it be hand because I can't reliably guess it. The exception being that I know I have 60+ rows on my terminal so I will use that to estimate for very large marco playbacks. As a bonus, I'm going to suggest everyone learn about :h gn which make it easy to do . repetition on search matches. See vimcasts.org/episodes/operating-on-search-matches-using-gn
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An alternative approach:

If

  • your YAML structure has well defined fields to be used by your app
  • AND you may freely add additional fields that won't mess up with your app

then

  • at any level you may add a new block text field named like "Description" or "Comment" or "Notes" or whatever

Example:

Instead of

# This comment # is too long

use

Description: > This comment is too long

or

Comment: > This comment is also too long and newlines survive from parsing!

More advantages:

  1. If the comments become large and complex and have a repeating pattern, you may promote them from plain text blocks to objects
  2. Your app may -in the future- read or update those comments
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8 Comments

I guess this is the holly grail answer to the question; especially if one wants these comments to appear in JSON or XML if one is to transform from YAML to these two.
this is like those var comment = 'this code does stuff'
@mTvare Programming languages approach commenting in a different way of thinking than data serialization languages. A specific pattern that looks stupid in a domain, could be the best choice in another.
foo: bar # this is a comment, too
You might have an app that validates against a schema and complains about unrecognised fields.
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One way to block commenting in YAML is by using a text editor like Notepad++ to add a # (comment) tag to multiple lines at once.

In Notepad++ you can do that using the "Block Comment" right-click option for selected text.

Woo Images!

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3 Comments

This is not the only way.
And FWIW, the keyboard shortcut for that (in np++) would be ctrl-shift-Q (on windows. For other platforms, see the edit>comment/uncomment menu).
For grammar-based questions, a correct answer only needs to discuss the grammar. Other details about a particular tool (such as a particular text editor) are unnecessarily specific and thus inapplicable to the question as asked.
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Emacs has comment-dwim (Do What I Mean) - just select the block and do a:

M-;

It's a toggle - use it to comment AND uncomment blocks.

If you don't have yaml-mode installed you will need to tell Emacs to use the hash character (#).

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2 Comments

Again, the OP asked a simple YAML grammar question, not a text editor question. (Imagine if every general language question included answers coupled to all the editors in use... maybe some people want such a world, but that isn't the design of StackOverflow.)
Most of us know there is no such thing as block-comment in YAML. I'd suggest that at this point we edit the question to "How does one comment out multiple lines in a YAML file with different editors/tools" instead. That way we keep the answers here useful while we answer both the original question and provide suggestions to people to get the job done.
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For RubyMine users on Windows:

  • Open the file in the editor.

  • Select the block and press:

    Ctrl + /,

  • And you will have the selected block starting with #.

Now if you want to uncomment the commented block, press the same key combination Ctrl + forward slash again.

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2 Comments

That works for all JetBrains IDE's I think. I know it works for PyCharm as well :) Works on Mac OSX as well.
It is better to answer a grammar question directly, without unnecessarily mentioning a text editor. (I would make a very rough guess that there are at least 25 widely used editors, very roughly defined as having over 50,000 users per year.) On the other hand, there is only one dominant edition of YAML -- the 3rd edition -- released in 2009.
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In the Azure DevOps browser (pipeline YAML editor),

Ctrl + K + C Comment Block

Ctrl + K + U Uncomment Block

There also a 'Toggle Block Comment' option, but this did not work for me.

Enter image description here

There are other 'weird' ways too: Right-click to see 'Command Palette' or F1

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Then choose a cursor option.

Enter image description here

Now it is just a matter of #.

Or even smarter [Ctrl + K] + [Ctrl + C]

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5 Comments

I interpret the question as asking how to do a block comment in any YAML file; therefore, answers should not be coupled to any particular tool.
@david j, is that even possible not to mention a tool? In any of these answers?
Yes: a correct answer only needs to discuss the YAML grammar. See the other answer at stackoverflow.com/a/2276604/109618. Other details based on the specific text editor used are unnecessarily specific and thus inapplicable to a general audience.
Those who end up on this link are those who are using a text editor. Clearly the one you pointed out has 2000+ votes which of course is the right answer. But the one with 159 votes is about sublime editor and there are many others on different tools. Or in other words you have more downvotes to do.
The StackOverflow UX workflow is somewhat constraining, but this is by design. It is designed to promote direct answers to the asked question, not dozens of different answers based on tooling.
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If you are using Eclipse with the YEdit plugin (an editor for .yaml files), you can comment-out multiple lines by:

  1. selecting lines to be commented, and then
  2. Ctrl + Shift + C

And to uncomment, follow the same steps.

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1 Comment

Again, the OP asked a YAML grammar question, not a text editor question.
-17

In a .gitlab-ci.yml file, the following works:

To comment out a block (multiline): Select the whole block section > Ctrl K C

To uncomment already commented out block (multiline): Select the whole block section > Ctrl K U

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5 Comments

That keyboard shortcut will work for some specific editor, not some specific YAML file.
@Quentin I mentioned gitlab yaml file and not any other yaml file. One can access and update .gitlab-ci.yaml file on gitlab interface on any browser.
So this is specific to the Gitlab browser-based editor and a specific file? Doesn't seem to be a very useful answer to a general question about YML files.
Yes. Question was general and it did not mention specific editor or environment. Others gave their observations w.r.t. to their editors like notepad++, sublime text, Azure pipeline editor etc. My observation was w.r.t. to gitlab yaml file on gitlab environment which has its own pipeline editor. Could be useful for someone working on gitlab yaml file in gitlab environment.
thanks @vinsinraw, helped me with GitLab editor

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