> For the complete documentation index, see [llms.txt](https://docs.specgen.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.specgen.io/readme.md).

# Introduction

Specgen allows developers to write specification of HTTP API and/or JSON models.

Specgen provides good quality code generation for HTTP service, client and models code. This is full implementation of API-first approach. API creation/changes happens first in the formal API specification and then these changes automatically reflected in the code.

The documentation is split into following sections:

## spec

Section [spec](/spec/format.md) describes spec format language and all aspects of it.

## specgen

Section [specgen](/specgen/overview.md) describes code generation features. It also includes documentation for all build plugins.