How to disable mobile input auto zoom like some websites and Stack Overflow

On iPhone if text input’s font-size is less than 16px, it automatically zooms in. I didn’t wanted to add since its not recommended, but tried the meta viewport hacks, but it didn’t worked too, here is my viewport:

<meta name="viewport" content="width=device-width, height=device-height, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1, user-scalable=no" />

But I’ve saw many websites that has input less than 16px and it doesn’t zoom in to input on my mobile, even without viewport values user-scalable=no or maximum-scale=1 and one of that websites is Stack Overflow.

Stack Overflow example here with 13px input size and doesn’t has particular viewports tags that every post on internet says its needed to disable input zoom in.

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Is there some knowledge that passess in secret to disable this zoom? I’ve checked many articles but all of them is limited to what I tried/mentioned above. I’m guessing there might be a JavaScript hack for this but my attempts of preventDefault on focus, click etc. failed.