schema

schema is an open-source tool by Deyan Dobrinov that reads a committed structure.sql, MySQL dump, SQLite schema or Rails schema.rb and renders it as an interactive entity-relationship diagram. It also shows how the schema changed between git refs as a visual diff. A single Rust engine compiled to WebAssembly powers the CLI, the browser viewer and embeddable HTML diagrams. The latest release listed is v0.7.0.

What It Is

schema is a command-line tool that starts a local viewer for the schema file in your repository. Run schema in a repo and it opens a diagram of db/structure.sql or db/schema.rb, showing uncommitted changes if any. It needs no database connection, app boot or account, and the README states that schemas are parsed and laid out locally.

Git-aware schema diffs

You can compare the working tree, the index, commits, branches or tags using git ref syntax such as main...feature, or compare two files with --base-file. Added tables and columns are shown in green, removed ones in red and dashed, and changed ones in amber with old → new types. Comparisons open on the changed tables only, and neighbours can be added. Enum changes appear as nodes linked to the columns that use them. schema diff outputs a Markdown or JSON summary for pull requests.

Focusing and exporting

Large schemas can be narrowed with focus tables and neighbour depth, include/exclude globs, hidden columns, column modes and custom groups. Layouts include layered, force-directed, grid, circular and radial, with orthogonal, curved or straight edges. Named views can be saved in .schema.json. Output can be exported as SVG, PNG or a self-contained HTML file, and an embed script mounts diagrams in any page.

Design mode and agent skills

Design mode lets you sketch new tables, columns, foreign keys and indexes on top of the real schema, view them as a diff, and export a spec that an agent implements as migrations; schema design check verifies the result. Bundled skills for Claude Code and other agents (/schema-view, /schema-diff, /schema-inspect, /schema-embed, /schema-design) open diagrams, review migrations for risks, answer schema questions and generate HTML docs.

Setup path

Install with Homebrew, download binaries for macOS, Linux or Windows from the releases page, or build from source with Rust and wasm-pack. Git must be on the PATH for git-related features. A browser playground lets you try it without installing.