I use the wonderful WP-CLI tool. Due to dependence on Apache environment variables for a specific use case, I need to enable a bit of code to run only when running under WP-CLI. How can I detect if WP is running under WP-CLI?

In this specific case I could check for the presence of the Apache environment variables in question. However, I would like to know the more general, canonical method to check. Thank you.

2 Answers 2


Within the php/wp-cli.php we find these lines:

// Can be used by plugins/themes to check if WP-CLI is running or not
define( 'WP_CLI', true );
define( 'WP_CLI_VERSION', trim( file_get_contents( WP_CLI_ROOT . '/VERSION' ) ) );
define( 'WP_CLI_START_MICROTIME', microtime( true ) );

so you could check if WP_CLI or WP_CLI_VERSION are defined.

  • 8
    WP_CLI is the preferred constant to check May 10, 2016 at 11:55
  • Thanks for commenting - yes and also much shorter, was just wondering about other possibilities ;-) @DanielBachhuber
    – birgire
    May 10, 2016 at 12:27
  • @dotancohen you should consider accepting the answer by Ryan McCue instead, as it shows explicitly how to check it.
    – birgire
    May 10, 2016 at 14:20
  • @birgire, may I ask you to have a look at a custom field related question here : wordpress.stackexchange.com/questions/265852/… ? May 4, 2017 at 19:36

The canonical check for WP-CLI, which is used in most plugins and is explicitly mentioned in the docs, is the check whether WP_CLI is defined and set to true:

if ( defined( 'WP_CLI' ) && WP_CLI ) {
    // Do WP-CLI specific things.

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