to be honest, I do not understand your question. Do you want to implement a captcha for ownCloud logins or are you using an ownCloud instance where a captcha is required? If the latter is your issue you cannot do nothing, when this is not a cloud you are running by yourself.
thank you very much for returning back to me. My question in short form is that "Is there any solution other than captcha while signing in to owncloud system?
In long form : When a user uses the link provided by us to download his/her data from the cloud system user faces with a login page. On this page the user uses uses credentials (User ID and Password) to log in to system. Am I right? On this page, I mean on the page user sign in to cloud system there is a captcha verification system to prove that the applier is a human not a robot.
My quesiton is that is there any other solution we can use for this verification other than captcha?
@dervisali Hcaptcha isn’t part of the default ownCloud product. I’d assume it was added by your organisation. Other login methods can be configured from admins. You could also login with OpenID Connect or use various 2-Factor (2FA) login methods.