Nest Devtools alternative: nestjs-doctor, free and open source

nestjs-doctor is a free, open-source static analysis tool for NestJS. It is an MIT-licensed alternative to Nest Devtools for the module graph, the boot timings and the CI report. It reads the @Module() decorators from source, so nothing boots and nothing about your code leaves your machine, and adds rules across five categories and a 0-100 score. The one thing it cannot do is show the graph Nest built at runtime.

Both tools draw a NestJS module graph and get there from opposite ends: Nest Devtools boots your application and introspects the graph Nest built. Neither approach contains the other, so this page covers what each one can see.

nestjs-doctor takes one command:

npx nestjs-doctor@latest . --report

That writes a single HTML file and opens it. Nothing boots, so a module that cannot start, because a provider is missing, still shows up in the graph with the problem named.

Nest Devtools takes a DevtoolsModule import plus a snapshot flag on NestFactory.create. The running app then exposes an extra HTTP server, on port 8000 by default, and the dashboard at devtools.nestjs.com reads the graph from it. Nest's own documentation says not to enable the module in production.

Both show you where startup went. Devtools has a bootstrap performance analyzer. --timings overlays per-class construction times on the module graph in the report.

They read the same artifact. --timings takes the SerializedGraph that Nest itself produces, which is the same dump Devtools introspects, so a Devtools user already has what it needs. Boot trace covers capturing one.

This is the widest gap, and it runs both ways at first glance. Devtools does analyze your graph, and its findings carry error, warning and info severities. There are 11 checks, all architecture heuristics, with thresholds fixed in the product.

nestjs-doctor runs rules across security, correctness, architecture, performance and schema. Every one can be disabled, ignored per line, or replaced, and you can add your own against your own conventions.

See Rules for the full list and Custom rules for writing one.

The Devtools graph is Nest's injector graph: modules, classes, entrypoints. It has no concept of a database.

nestjs-doctor extracts an entity-relationship diagram from Prisma, TypeORM, Drizzle and MikroORM, and reports three schema rules against the entity itself. Schema rules covers what it checks.

Devtools publishes serialized graphs to a central registry and shows a diff between builds. That integration sits on the Enterprise plan, and it reports rather than gates.

nestjs-doctor is built to fail a build. --blocking gates on severity, --min-score gates on the score, and the GitHub Action comments only on what a pull request introduced. Failing the build covers the flags.

No. Nest Devtools is a paid product with a free trial, and its CI integration sits on the Enterprise plan. nestjs-doctor has no paid tier and no seat count. Everything ships under MIT, and that includes the parts Devtools charges for: the module graph, the boot timings and the CI report.

Under MIT:

• The CLI and every built-in rule, plus the rules you write yourself.
• The HTML report: module graph, endpoint traces, ER diagram and boot trace.
• The GitHub Action that reviews pull requests.
• The VS Code extension and the language server.
• The skills for coding agents.

nestjs-doctor is a free, open-source alternative to Nest Devtools for the module graph and CI. It is MIT licensed and reads your source instead of booting the app. It adds rules across five categories, a 0 to 100 score and an ER diagram; Devtools has 11 checks, no score and no database view. It cannot show the graph Nest built at runtime.

Other free tools in the Devtools space watch a running app: request, query and exception monitors, and MCP bridges that hand a running app's routes and logs to an AI assistant. They read what the app does at runtime, so they run alongside nestjs-doctor, not instead of it. The NestJS ESLint plugins are static like nestjs-doctor, and that page lists where they overlap rule for rule.

Nothing here requires a choice. DevtoolsModule stays in your app for the runtime questions, and nestjs-doctor runs in CI on every pull request, where Devtools does not gate anything.

Start with a scan and read the score:

npx nestjs-doctor@latest .

Quickstart covers reading the output, and GitHub Actions setup covers putting it on pull requests.