Hey,
It’s the default permalink structure in WordPress. If you prefer to use pretty permalinks, go to Settings → Permalinks and select Post Name in the Permalink Structure, as shown in the screenshot below. This should resolve the issue. However, the default permalink will still work in the background.
Give it a try, and let me know how that goes! 😄
Just to add, the default ?p=[post-id] will always work, no matter which permalink structure you choose. WordPress will ensure that your preferred permalink structure is reported to search engines as the canonical URL.
The default structure should definitely not 404 though. Try re-saving your permalink structure at Settings > Permalinks in your Dashboard. If WordPress cannot automatically edit the .htaccess file, it will provide manual instructions after saving.
Thank you for your replies.
Actually it is working exacly as I want: if you try to open a ?p8428 it will bring you to a 404 page on my website, and the /post-title is working perfectly.
I just realized that I have hundreds of ?p*** (revisions, drafts, media, etc), that are noindex and nofollow as I sat up with seo options.
But as you confirmed that default structure with ?p-id will anyway be created, then you solved my doubt.