I am interested to hear the consensus from HN users as to which is better, and why.
E.g. blog.example.com pointing to a static website while project.example.com points to a server.
If you want both to be under the same domain and use a CDN for only one of them, you still have to configure the pass through of all others... But if it's only one subdomain, CloudFront no longer needs to know about non-Cloudfront endpoints.
I run my Hugo site on S3+CloudFront for a be penny a month (if that), despite also having a $5/month server... It protects my site from going down if one if the 5 WP sites I lazily host for friends gets directly attacked and someone pops a shell + container break out.
The basic distinction, from a purely SEO perspective, is that blog.domain.com will be treated as its own entity whereas domain.com/blog will be treated as part of the main domain.com entity.
The question you have to ask yourself is whether you want to bolster the "value" of your main domain or if you want your blog to be an asset in its own right.
There is no right or wrong answer — there is simply what's best for your situation.
This has been fairly well beaten into the ground at this point.
Security-wise, a subdomain can also be a different origin. Which is often positive, so a flaw in your blogging software doesn't allow someone to extract cookies or so from the main site.
This is why using a completely separate domain can be wise if you’re using a third party to host your blog. At Fastmail when we shifted our blog to Ghost(Pro), we moved the blog from blog.fastmail.com to fastmail.blog, so that they definitely can’t get any cookies we may happen to set on domain=fastmail.com (even though our login cookies are domain=www.fastmail.com and thus safe anyway; defence in depth, and all that; by contrast, our product Topicbox does store its cookies on domain=topicbox.com, so the protection of using topicbox.blog is real there).
For your blog, it doesn't matter. You can hard-code the entire URL in every link and it will probably never go wrong. Applications are harder. Applications that various people are going to self-host are hardest.
In general I would think that it is to create contents and SEO, in which case I believe that it is better to host it under the website's domain. On the other hand you may be targeting a different audience from your main site/product. For example Uber, Netflix at al have "engineering blogs" these days, which clearly have no relation to their product but perhaps rather aimed at being a recruitment tool. In such case you might want to use different domains (which incidentally is what both Uber and Netflix do).
I see people commenting on the technical aspects but the differences are minor and the business goals should be driving the decision.
Of course, you can have a load balancer under example.com that acts as a reverse proxy for your forum unter example.com/forum, but the easier setup with different languages/software/servers is to use subdomains imho.
- You don't have to add and manage subdomain
- You don't have to stop and restart the reverse-proxy of your VPS
- Only one cert to deal with (I use traefik w/ automatic LE renewal but that implied more things to set up on the chain)
But I still use blog.domain.com because I find it prettier. And when I need to type it in the URL bar it's just $service<tab>.domain<tab><enter>.
Now the SEO crowd has other requirements that make their choice more valid than my own (one user, one set of idiosyncrasies).
That provides protection for if someone manages to get a malicious script into your blog, they can't start making authenticated requests (since it isn't the same origin).