🔧 Configure your hook

Old schema file path The schema file at the base branch or previous state.

New schema file path The schema file in your working tree. Can be the same path if it changes during development.

SQL dialect

Output format

Hook style

Plain git hook works in any repo. pre-commit framework is for Python/pre-commit users and keeps hooks versioned.

Fail the commit if breaking changes are detected

Use staged copies of schema files (recommended)

.git/hooks/pre-commit

⚡ How to install

1

Save the hook

For the plain git hook, save it to .git/hooks/pre-commit and make it executable: chmod +x .git/hooks/pre-commit. For the pre-commit framework, add the YAML to .pre-commit-config.yaml.

2

Commit a schema change

The hook runs automatically when you commit any file. It diffs your configured schema paths and prints a summary to your terminal.

3

Block breaking changes

With "Fail on breaking" enabled, the commit is rejected if SchemaLens detects dropped tables, columns, or other risky changes.

🛡️ What it catches

🔴 Breaking changes

Dropped tables, dropped columns, type changes, and removed constraints block the commit.

🟡 Safe migrations

Added tables, columns, and indexes pass through with a clear report.

📊 Risk score

Every diff gets a 0–100 risk score so reviewers know what to prioritize.

🔒 Privacy first

Schema files are sent to SchemaLens for diffing; no database connection required.

Schema Diff Pre-commit Hook Generator