Target: X (Twitter), Bluesky, and/or Mastodon. Pick one primary, cross-post to the others. When: the same day as the Show HN post, 2-3 hours after HN goes up (so the HN link is already in the wild) Tone: build-in-public, technical, no marketing speak. The point of the thread is to make the process interesting, not to sell the product.
1/8
I spent 2 years building a site with 562 free browser-side tools.
Mortgage calculator. BMI. Compound interest. Password generator. BPM tapper. JSON formatter. Eyepiece calculator. Invoice generator. Sleep cycle planner. Colour contrast checker.
550+ more. All free. All in the browser. No accounts, no display ads, no upsell.
Here's how ↓
[link to the site]
2/8
The architecture is intentionally boring.
• 562 separate HTML files, one per tool • 1 JSON file with all 562 entries • 1 home page that reads the JSON • 1 build script that regenerates the sitemap, RSS, and embed page from the JSON
No npm. No framework. No build step. Total repo: 47 MB.
3/8
The most-interesting engineering decision was the no-display-ads part.
View source on any page on the site. You will not find an ad slot, an ad network script, a sponsored-content block, or a retargeting pixel. The whole markup is the page, and the page is the tool.
This caps the addressable audience (I can't do paid acquisition). I think it's the right call. (The third-party scripts on the site are Google Analytics, for measurement, and three.js / cannon.js / the YouTube IFrame API on the specific tool pages that need them. None are advertising.)
4/8
The math tools are the part I am proudest of.
The “How mortgages really work” guide walks through the standard repayment formula, the three things the bank's calculator never shows you, and the honest way to use the numbers.
Banks show you the monthly payment. The guide shows you the total interest over 25 years. It's a £40k difference.
5/8
The catalogue as data.
cards.json is exposed. related.json is exposed. llms.txt is exposed. .well-known/ai.txt says “AI engines can cite this site”.
The first AI citations started showing up 2 weeks after I added the definitive guides. The site is being read as a source, not just a page.
6/8
The embed feature is the under-rated part.
/embed.html lets you iframe any tool in one line. A non-profit health clinic has the BMI calculator on their resources page. A primary school has the times-tables tool on theirs.
About 30% of traffic now comes from embeds.
7/8
The numbers.
562 tools. 47 MB repo. £8/month hosting. £34.50 in donations over 9 months. 30 outside contributors. 12 long-form guides. 3 blog posts. 1 person, evenings and weekends, in Luton, UK.
The site is not a startup. It is a hobby that has grown.
8/8
If you only click one thing on the site, click this:
https://www.themostusefulsiteintheworld.com/guides/mortgage.html
It's the guide I am proudest of. The bank's calculator never tells you the total interest. This one does.
Repo: https://github.com/mrpr0phecy/mrpr0phecy
Happy to answer questions.
Bluesky's character limit is the same as X (300), so the thread works as-is. The tone is already technical and link-friendly. One change: Bluesky audiences skew more toward open-source and indie-web, so lead with the “no display ads” or the “open source” tweet if you want to pick a different tweet #1.
Mastodon has a 500-character limit per post. The thread works as-is, but you have room to expand each tweet. The indieweb/Mastodon audience will appreciate a longer post #1 that includes the link to the repo as well as the live site.
After 48 hours, record in INCOME.md: