What is the difference between yaml and yml extension

Question

I read them on YAML-wikipedia but not really understood the main difference between them  I saw there are someone using  yaml extension  however  Symfony2 use  yml extension    YAML is a human-readable data serialization format that takes concepts from programming languages such as C  Perl  and Python  and ideas from XML and the data format of electronic mail   YAML is a recursive acronym for  YAML Ain t Markup Language   Early in its development  YAML was said to mean  Yet Another Markup Language   3  but it was then reinterpreted  backronyming the original acronym  to distinguish its purpose as data-oriented  rather than document markup   So  how exactly the different between  yaml and  yml  When should we prefer one over the other

User · Accepted Answer

File extensions do not have any bearing or impact on the content of the file. You can hold YAML content in files with any extension: .yml, .yaml or indeed anything else.

The (rather sparse) YAML FAQ recommends that you use .yaml in preference to .yml, but for historic reasons many Windows programmers are still scared of using extensions with more than three characters and so opt to use .yml instead.

So, what really matters is what is inside the file, rather than what its extension is.

User · Answer

As  David Heffeman indicates the recommendation is to use  yaml when possible  and the recommendation has been that way since September 2006    That some projects use  yml is mostly because of ignorance of the implementers documenters  they wanted to use YAML because of readability  or some other feature not available in other formats  were not familiar with the recommendation and and just implemented what worked  maybe after looking at some other project library  without questioning whether what was done is correct    The best way to approach this is to be rigorous when creating new files  i e  use  yaml  and be permissive when accepting input  i e  allow  yml when you encounter it   possible automatically upgrading correcting these errors when possible   The other recommendation I have is to document the argument s  why you have to use  yml  when you think you have to  That way you don t look like an ignoramus  and give others the opportunity to understand your reasoning  Of course  everybody else is doing it  and  On Google  yml has more pages than  yaml  are not arguments  they are just statistics about the popularity of project s  that have it wrong or right  with regards to  the extension of YAML files   You can try to prove that some projects are popular  just because they use a  yml extension instead of the correct  yaml  but I think you will be hard pressed to do so   Some projects realize  too late  that they use the incorrect extension  e g  originally docker-compose used  yml  but in later versions started to use  yaml  although they still support  yml   Others still seem ignorant about the correct extension  like AppVeyor early 2019  but allow you to specify the configuration file for a project  including extension  This allows you to get the configuration file out of your face as well as giving it the proper extension  I use  appveyor yaml instead of appveyor yml for building the windows wheels of my YAML parser for Python      On the other hand       The Yaml  sic   component of Symfony2 implements a selected subset of features defined in the YAML 1 2 version specification     So it seems fitting that they also use a subset of the recommended extension

[symfony] What is the difference between .yaml and .yml extension?

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