Ask HN: Tech blog – Why to do it and what to write about?

I think it comes down to what you want to achieve

I have a tech blog as my tech notebook. After years of loosing notebooks Ive found a blog the best solution to this.

So when I solve a problem I will write it up and then if its useful to others then fine

Keep it simple. Just write about things that you find interesting. It could be a new library/tool/framework that you used/built or how you solved a particular problem. What you genuinely find interesting is likely to be useful for other developers as well. E.g. I maintain this blog: https://blog.amirathi.com/

Building a technical blog answers the question "How?" I think you want to focus on "Why?" What is it that you want to achieve? Do you want to become famous, become seen by a group as an expert, make money? Think about the "Why?" and the "What?" should become a bit more obvious.