A study hall
for systems work.
Semicolony is a working desk for software engineers — a single site that gathers the daily utilities, the interactive models, the long-form reading, the structured roadmaps, and the cited measurements that keep the day moving. Less opinion than a blog, less weight than a textbook, less noise than a Google search.
Six rules we don't break.
Semicolony is opinionated about the boring parts so the content can be flexible about the rest. These six are not preferences — they are constraints.
- 01
Local by default.
Every tool runs in your browser. The data you paste, type, or upload never leaves the tab unless we say otherwise — and even then, optionally.
- 02
No account required.
No login, no sign-up, no key. Bookmark the page, share the URL, link to a section. The site is a reference, not an app you live inside.
- 03
Linkable everywhere.
Sections, examples, simulator states — all are URL-addressable. The whole site is meant to be cited from team docs and revisited on real problems.
- 04
Cited or unwritten.
The Lab Notebook holds the measurements; the handbook lists the papers. If a number is not citable, it is not in the body — it is in the chapter that says "rough estimate."
- 05
Aggregate analytics, nothing personal.
Google Analytics with IP anonymisation runs on every page — page path and referrer, nothing more. No cross-site tracking, no advertising joins, no input capture. Block it with uBlock Origin if you want; the site works the same.
- 06
Reference shape, not blog shape.
Pages are written to be re-opened. Less personality, more structure. The scaffolding is intentional: lede → body → further reading, each time.
Fourteen shelves, one library.
The site is laid out as a small reference library. Four primary surfaces are in the masthead — Tools, Guides, Simulators, Handbook — and the rest live under the Library dropdown next to them. The roadmaps tie them together into ordered learning paths.
Structured learning paths — backend, system design, frontend, DevOps, security, DSA, data.
read →Daily-use utilities — every one runs locally.
read →Long-form deep-dives into the systems engineers use.
read →Interactive widgets that let you push the buttons.
read →A system-design curriculum — modules, not pages.
read →Reproducible benchmarks and cited measurements.
read →The maths and physics under it all.
read →A cabinet of shapes, with operations and Big-O.
read →Every term in Semicolony, A-Z.
read →Printable references for the things you forget.
read →Annotated reading list — what to study, why.
read →The system builders behind the names.
read →Famous outages, narrated.
read →Foundational CS papers — annotated, with context.
read →No ads, no other strings.
Semicolony currently runs no advertising at all — no ad network, no ad slots, no ad cookies. The whole site is free, with nothing gated, throttled, or held back.
No tracking pixels, no autoplay video, no popovers, no interstitials, no newsletter modals, no "subscribe to read more." Every page works the same whether you have an ad-blocker on or off, because there is nothing extra to block. Nothing on this site sits behind a paywall.
If ads are ever added to help cover hosting, they'll be a few unobtrusive slots, documented plainly on the privacy page first — funding, never a gate. If anything ever feels wrong on a page, flag it via @semicolonydev.
How to get in touch.
Email hello@semicolony.dev for corrections, broken-link reports, factual fixes, removal requests, licensing questions, or anything else. Reasonable requests answered within a few days. On X: @semicolonydev.
Three good opening moves.
A curated front page with the most-used tools and most-popular guides. Designed to bookmark.
go to homepage →15 long-form modules on system design — caching, sharding, scaling, design framework. Fully cross-linked.
open the handbook →Press ⌘K from any page. Local index, no API call. 200+ entries indexed.
open search →