on-the-fly validation code

noun
UK /ɒn ðə flaɪ ˌvælɪˈdeɪʃən kəʊd/
US /ɑn ðə flaɪ ˌvælɪˈdeɪʃən koʊd/

Code that checks something right away while you are typing or using it.

The sign-up form uses on-the-fly validation code to tell you instantly if your email is wrong.

SYNONYMS

real-time validation codeinstant checking codelive validation scriptimmediate verification code

RELATED WORDS

form validationinput checkingerror messageuser feedbackweb form

OTHER MEANINGS

2. Code that checks data as it is being entered rather than after the whole form is submitted.

Instead of waiting for the submit button, the app runs on-the-fly validation code on each field.

3. Programming logic that verifies a value at the moment it is used, without a separate checking step.

The API applies on-the-fly validation code to every request before saving it.

4. Quick checks built into a program that catch mistakes early and warn the user immediately.

Thanks to on-the-fly validation code, the password strength bar updates as you type.