Case Insensitive String parameter in schema of openApi

Here's a copy of my answer to the same question on Stack Overflow:

Enums are case-sensitive. To have a case-insensitive schema, you can use a regular expression pattern instead:

- name: platform
  in: query
  description: 'Platform of the application. Possible values: `desktop` or `online` (case-insensitive)'
  required: true
  schema:
    type: string
    pattern: '^[Dd][Ee][Ss][Kk][Tt][Oo][Pp]|[Oo][Nn][Ll][Ii][Nn][Ee]$'

Note that pattern is the pattern itself and does not support JavaScript regex literal syntax (/abc/i), which means you cannot specify flags like i (case insensitive search). As a result you need to specify both uppercase and lowercase letters in the pattern itself.

Alternatively, specify the possible values in the description rather than in pattern/enum, and verify the parameter values on the back end.