Error map

How the 45 categories and 1,481 errors connect — and where in a request each one happens.

How the categories connect

Each dot is a category (bigger = more errors), placed in the layer where its errors usually happen. A line means pages in the two categories link to each other — thicker lines mean more links. Hover a dot to follow its connections; click to open the category.

Where do errors come from?

The seven layers a request passes through. Find the layer first — then you know which category to search.

1. 1

   On your device

   320 errors

   Errors raised in the browser, the app or UI code — before the request leaves your machine, or while the page is being drawn.

   Looks like: TypeError: x is undefined · ERR_BLOCKED_BY_CLIENT · layout overflow · permission denied

   Browser53 JavaScript50 TypeScript3 React51 Angular53 Vue3 Next.js3 Flutter / Dart3 Android50 iOS51
2. 2

   Network

   57 errors

   The request is travelling: DNS, TLS certificates, status codes and mail delivery decide whether it arrives.

   Looks like: ERR_CONNECTION_RESET · certificate invalid · 404 / 429 · SMTP 550

   HTTP51 SSL / TLS3 Email / SMTP3
3. 3

   Edge & web server

   53 errors

   CDNs, proxies and web servers sit in front of your app and answer with 5xx pages when the next hop fails.

   Looks like: 502 / 504 · Cloudflare 52x · upstream timed out · rewrite loops

   Cloudflare50 Nginx / Apache3
4. 4

   Application & API

   474 errors

   Your code: exceptions, type errors, framework misconfiguration, API contracts and login/token problems.

   Looks like: NullPointerException · 500 · JWT invalid · segmentation fault · class not found

   PHP50 Python53 Java50 Node.js52 .NET50 Go3 Rust3 Ruby / Rails3 C/C++53 Laravel3 WordPress50 API54 Authentication50
5. 5

   Data

   160 errors

   Databases and caches: connections, permissions, locks, constraints and memory limits.

   Looks like: Access denied · deadlock · duplicate key · too many connections · OOM

   SQL51 MySQL50 PostgreSQL53 MongoDB3 Redis3
6. 6

   Platform & cloud

   313 errors

   The machine and runtime underneath: containers, clusters, cloud permissions and the operating system.

   Looks like: CrashLoopBackOff · AccessDenied · permission denied · out of memory · blue screen

   Docker51 Kubernetes50 AWS51 Azure50 Google Cloud / Firebase3 Terraform3 Linux51 Windows51 macOS3
7. 7

   Build & delivery

   104 errors

   Getting code to run: version control, package managers and CI/CD pipelines.

   Looks like: merge conflict · ERESOLVE · npm install failed · pipeline step failed

   Git51 npm50 CI/CD3

Strongest connections

• Browser ↔ JavaScript 216 links
• API ↔ HTTP 200 links
• MySQL ↔ PostgreSQL 156 links
• Authentication ↔ Azure 134 links
• .NET ↔ Java 125 links
• Cloudflare ↔ HTTP 118 links
• Azure ↔ Docker 114 links
• AWS ↔ Azure 110 links
• Browser ↔ Cloudflare 110 links
• Docker ↔ .NET 108 links
• API ↔ MySQL 106 links
• Java ↔ Python 104 links