Justin Pirrie
Founder of ToolStack · builds the tools, writes the guides
I’m Justin Pirrie, the founder of ToolStack. I build every tool on this site and write every guide that goes with it.
ToolStack started from a simple frustration: the web is full of “free” tools that bury a calculator under three ads, gate the result behind a signup, or upsell you the second you get an answer. I wanted the opposite — tools that load instantly, do one job well, and never ask for your email. Today that’s 65+ tools across writing, SEO, development, and everyday utilities, all free and account-free.
I’m a builder first. Before I write about a tool, I build it and use it myself — which is why the guides here come from actually shipping these things, not from re-summarizing someone else’s article. When I explain how a UTM builder works or why a JWT is structured the way it is, it’s because I’ve implemented it.
Alongside ToolStack I work on AdvertsGPT, helping businesses get found in AI search — the shift from classic SEO to how ChatGPT, Google’s AI Overviews, and Perplexity decide what to cite. That work feeds straight back into ToolStack: a lot of these tools and guides exist because I needed them myself.
What I write about
Free web tools
Practical utilities that do one job, fast.
SEO & AI search (GEO/AEO)
Ranking in Google and getting cited by AI.
Marketing workflows
UTMs, email, content — the hands-on how-to.
Developer utilities
JSON, JWT, regex, encoding — explained clearly.