Subdomain or subpath for side project marketing?

If your building the app into an existing application. You may have no choice without some configuration on the server you may or may not have access too.

If this is totally separate, then building it as a subdomain is far better for many reasons.

Unless you have a compelling reason for subdomains, just go with the default, subpaths.

1. I have yet to read any compelling evidence that either is better than the other for SEO
2. Subpaths are the more common option probably because they are the default option, especially in website builders. Imagine 1/3 of websites are built using a website builder such as WordPress, Wix, Shopify, and Squarespace. When new content is added using a website builder, such as a new web page, or a side app, in this case, the website builder by default creates the new content as a subpath of the main domain. Creating a subdomain would require extra steps that people are less likely to take, especially if they don't know how to set up a subdomain or what a subdomain even is.

An example of subdomains in use is Wiki country-specific sites such as https://en.wikipedia.org/ and https://fr.wikipedia.org/.

There is a lot of misinfo out there on this. GOOG has said for a long time that they treat subdomains and subdirectories similarly m. Yet all the empirical data points to the superiority of subdirectories.

My take is is that working in a subdirectory makes your SEO efforts easier and more effective. Plus, you’re still depending on GOOG to detect that they’re related sites (as opposed to customer subdomains)… Why take even a little risk?!

I like subpath, but for a blog, it's often easier to use subdomain. Google claims it doesn't hurt SEO. https://www.youtube.com/watch?v=uJGDyAN9g-g

https://blog.t.ly/