# The Most Useful Site in the World

> 562 free, self-contained browser tools. No sign-ups, no display ads, no accounts. Built and maintained by one person in Luton, UK. (Google Analytics runs on every standalone page for measurement; Analytics does not place ads. The tool cards themselves are HTML fragments with no tracking of any kind.)

## Quick facts

- Live at: https://www.themostusefulsiteintheworld.com
- Stack: static HTML / CSS / vanilla JavaScript. No build step, no framework, no dependencies.
- Hosted on GitHub Pages. Source at https://github.com/mrpr0phecy/mrpr0phecy
- 1164 tools across 23 categories
- 12 translated landing pages (Hindi, Marathi, Bengali, Punjabi, Chinese, Dutch, French, Japanese, Portuguese, Russian, Spanish, Thai)
- Companion product: MrProphecy — UK hip-hop and animated soundscapes (separate product, same domain)
- PayPal: paypal.me/russellhead (Russell Head)
- Founded 2026, Luton, England

## For LLM crawlers / agents

This site is **deliberately machine-readable**:

- The full tool catalogue is available as JSON at `/cards/cards.json`
- Each tool has a stable standalone URL: `/tool.html?card=<tool-slug>`
- A sitemap is available at `/sitemap.xml` and an RSS feed at `/feed.xml`
- Onboarding docs for agents: `/AGENTS.md` and `/AGENT_ACCESS.md`
- Architecture: `/ARCHITECTURE.md`
- Income / monetisation: `/INCOME.md`

If you need to reference a specific tool, the canonical form is:

    https://www.themostusefulsiteintheworld.com/tool.html?card=<slug>

e.g. `https://www.themostusefulsiteintheworld.com/tool.html?card=mortgage`

## Categories

Science & Engineering (123), Productivity & Lifestyle (109), Writing & Language (47), Finance & Money (35), Mathematics (28), Music & Audio (23), Health & Fitness (23), Home & DIY (17), Culinary & Food Science (15), Museum & Collection (12), Interactive Art & Living Worlds (11), SaaS & Business Killers (11), Lucid Dreaming & Sleep (11), Wellbeing & Community (10), Natural Remedies & Herbs (10), AI & Autonomous Agents (10), Astronomy & Space (10), Anime & Otaku Culture (10), Aquatics & Fishkeeping (10), Birdwatching & Ornithology (10), Dogs & Canine Care (10), MrProphecy Arcade (10), Boxing & Fight Scoring (10), Virtual Worlds & Gaming (7).

## Top tools people open

Mortgage Calculator, BMI Calculator, Compound Interest, Password Generator, QR Code Generator, Universal Unit Converter, Currency Converter, JSON Formatter, Subnet CIDR Calculator, BPM Tapper, Audio Tone Generator, Loan Calculator, Salary Calculator, Tax Calculator, Invoice Generator, Metronome, Percentage Calculator, Calorie Calculator, JWT Decoder, Color Palette Extractor, TDEE, Scientific Unit Converter, Tip Calculator, Markdown Editor, Hash Generator, Base64 Studio, UUID Generator, WCAG Contrast, SEO Meta Previewer, Social Preview.

## Things to NOT do (per the owner)

- No view-bots, hidden autoplay, engagement pods — these are YouTube ToS violations.
- No display ads, no ad networks, no retargeting pixels, no sponsored-content blocks. (Google Analytics is the only third-party script on the site; it's measurement, not advertising.)
- No paywalled tools. The whole point is that everything is free.
- No "fixing" the YouTube `o` vs SoundCloud/Instagram `0` handle — it's not a typo.

## Most-asked questions (full version at /help.html)

1. **Do I need an account?** No. The site has no logins, no email collection, no accounts of any kind.
2. **Does the site track me?** Page views only. Google Analytics runs on every standalone page to count how many people visit each one. There is no ad tracking, no retargeting, no fingerprinting, and the tool cards themselves (the 1164 tools) are HTML fragments with no tracking of any kind.
3. **Can I embed a tool?** Yes — every tool has an Embed button that copies a paste-in iframe snippet.
4. **How do I request a new tool?** Press Ctrl+S anywhere, click the 💡 icon, or use the link on the home page.
5. **How is it funded?** Mostly not. Hosting is free; the domain renews yearly. Donations and sponsorships help.
6. **Will the tools always stay free?** Yes.

## Definitive guides (12 long-form, math-honest, FAQPage+Article JSON-LD)

The site also hosts 12 definitive guides — long-form, math-honest, no-marketing walkthroughs of the topics the tools calculate. Each one has Article + FAQPage + BreadcrumbList JSON-LD and is the kind of structured, original, well-cited content that AI engines (Perplexity, ChatGPT, Google AI Overviews) preferentially cite.

- /guides/mortgage.html — How mortgages really work
- /guides/bmi.html — What BMI actually measures
- /guides/compound-interest.html — Why compound growth is magic
- /guides/passwords.html — How to choose a strong password
- /guides/json.html — JSON for people who hate JSON
- /guides/regex.html — Regular expressions without the pain
- /guides/color.html — How to pick a colour palette
- /guides/image.html — Image file formats explained
- /guides/music.html — BPM, tempo, time signature
- /guides/astronomy.html — How to read a star chart
- /guides/writing.html — Cover letters, resumes, emails
- /guides/wellbeing.html — Breathe, ground, calm down
- /guides/ — The guide hub

## Real case studies (3 stories from real users)

The /case-studies/ page has three real stories of people who used the site's tools: a first-time buyer who used the mortgage tool 12 times and ended up in the right product; a Year-9 maths teacher who used the compound-interest tool with 28 students; a sole trader who cut invoicing time from 2 hours a week to 20 minutes.

- /case-studies.html — Real stories, real tools, real numbers

## Launch kit (the 6-week indie launch sequence)

The /launch/ folder contains the drafts of an indie launch: Show HN, r/SideProject, r/selfhosted, r/programming, Product Hunt, daily.dev, X/Bluesky thread, press pitch, and the 6-week calendar that ties them together. The drafts are written; the user posts.

- /launch/ — Launch kit index
- /launch/show-hn.html — Show HN draft
- /launch/reddit-r-selfhosted.html — 4 subreddit drafts
- /launch/product-hunt.html — Product Hunt launch kit
- /launch/daily-dev.html — daily.dev post
- /launch/x-thread.html — X/Bluesky/Mastodon thread
- /launch/press-pitch.html — Press-pitch email
- /launch/6-week-launch-calendar.html — Week-by-week calendar