# Read-Only Mode

This guide explains how to **enable and use the read-only mode** in EventSourcingDB. In this mode, **all write operations are disabled**, while **reads and queries continue to work as usual**. This is useful for **maintenance**, **upgrades**, **migrations**, or any scenario where writing should be temporarily or permanently disallowed.

## Enabling Read-Only Mode

There are **two ways** to activate read-only mode:

- **Via API call**: Send a **`POST`** request to the **`/api/v1/put-into-read-only-mode`** endpoint:

    ```shell
    curl \
      -i \
      -X POST \
      -H "authorization: Bearer <API_TOKEN>" \
      http://localhost:3000/api/v1/put-into-read-only-mode
    ```

- **Via command-line flag**: Start EventSourcingDB with the **`--read-only` flag**:

    ```shell
    ./eventsourcingdb run [...] --read-only
    ```

Once enabled, the database will **reject all write attempts**. The mode **cannot be disabled dynamically**. To leave read-only mode, **restart EventSourcingDB and do not provide the `--read-only` flag**.

## What Still Works

In read-only mode, the following operations remain **fully functional**:

- **Reading events** via the **[read API](/learn/tutorials/first-steps-with-eventsourcingdb/reading-events)**
- **Observing events** via the **[observe API](/learn/tutorials/first-steps-with-eventsourcingdb/observing-events)** (though no new events will arrive)
- **Running [EventQL queries](/docs/eventsourcingdb/v1.1/eventql)**

This allows you to continue processing projections, audits, and analyses without interruption.

## What Is Disabled

The following operations are **blocked** while read-only mode is active:

- **Writing** new events
- **Registering** new schemas
- Any other operation that **modifies stored data**

Clients attempting these operations will **receive an error response** indicating that the system is in read-only mode.

## Typical Use Cases

Read-only mode is helpful in a variety of operational contexts, including:

- **System maintenance**: Prevent accidental changes during backups or inspections.
- **Upgrades and migrations**: Freeze the system state to ensure consistency while transitioning to a new version.
- **Kiosk or analytics deployments**: Serve data without risk of mutation in dedicated read-only environments.

## Operating Safely in Read-Only Mode

Read-only mode provides a **simple but effective safeguard** when write access must be suspended. It helps **protect data integrity** while preserving access for consumers, dashboards, and downstream systems.

Use it to keep your system **transparent** and **stable** – even when changes are not allowed.