Trailing slash redirect not happening, returns 200 instead

Hi, for some reason I can’t understand, on our website, addresses without trailing slash are not redirecting to the address with trailing slash, instead being served with a 200.
This results in duplicated content in the eyes of Google, which is not great.

Example: https://www.digitalspiders.io/sanity
Expected: 301 redirect to https://www.digitalspiders.io/sanity/
Result: page served with 200 at https://www.digitalspiders.io/sanity (then Gatsby changes the url to add the slash, but that’s not the same)

The weird thing is we have built dozens of websites for clients and those I tested all do the redirect correctly (https://heedcap.com/golden-visa), and our websites uses mostly the same code.
I wouldn’t put it past me that I made some change somewhere that would result in this, but I can’t fathom what it might have been.
I’ve checked that file structure in the build, and it looks the same as all other websites (index.html inside the folders). According to this guide, it should work.

Can anyone give me at least some pointers where to look?

Site name: digital-spiders-website-2880f9
Build without redirects: 6717a4f03c344b0008214ccf (probably any on this website)

Have you tried using Pretty URLs: Build & deploy | Site configuration | digital-spiders-website-2880f9 | Netlify?

@hrishikesh Not yet, but we’ve never activated it on any of our other websites, so that doesn’t help understand the difference.
Might try anyway as soon as I have a chance.

Pretty URLs is on by default as far as I’m aware.

Ok, I have no idea how I checked this, but you’re totally right, we actually had Pretty Urls activated everywhere but on our own website, and as soon as I activated it and redeployed, it started redirecting correctly.

Thank you for the guidance, and apologies for the lack of attention on my previous reply.