Set Up Logs

Structured logs allow you to send, view and query logs sent from your applications within Sentry.

With Sentry Structured Logs, you can send text-based log information from your applications to Sentry. Once in Sentry, these logs can be viewed alongside relevant errors, searched by text-string, or searched using their individual attributes.

Logs for Dart are supported in Sentry Dart SDK version 9.0.0 and above.

To enable logging, you need to initialize the SDK with the enableLogs option set to true.

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await Sentry.init(
  (options) {
    options.dsn = "___PUBLIC_DSN___";
    // Enable logs to be sent to Sentry
    options.enableLogs = true;
  },
);

Once the feature is enabled on the SDK and the SDK is initialized, you can send logs using the Sentry.logger APIs.

The logger namespace exposes six methods that you can use to log messages at different log levels: trace, debug, info, warning, error, and fatal.

Aside from the primary logging methods, we've provided a format text function, Sentry.logger.fmt, that you can use to insert properties into to your log entries.

These properties will be sent to Sentry, and can be searched from within the Logs UI, and even added to the Logs views as a dedicated column.

When using the fmt function, you must use the %s placeholder for each value you want to insert.

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Sentry.logger.fmt.error('Uh oh, something broke, here is the error: %s', [
  errorMsg
], attributes: {
  'additional_info': SentryLogAttribute.string('some info'),
});
Sentry.logger.fmt.info("%s added %s to cart.", [user.username, product.name]);

You can also pass additional attributes directly to the logging functions, avoiding the need to use the fmt function.

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Sentry.logger.error('Uh oh, something broke, here is the error: $errorMsg',
    attributes: {
      'error': SentryLogAttribute.string(errorMsg),
      'some_info': SentryLogAttribute.string('some info'),
    });
Sentry.logger.info('User ${user.username} added ${product.name} to cart.', attributes: {
  'user': SentryLogAttribute.string(user.username),
  'product': SentryLogAttribute.string(product.name),
});

To filter logs, or update them before they are sent to Sentry, you can use the beforeSendLog option.

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await Sentry.init(
  (options) {
    options.dsn = "___PUBLIC_DSN___";
    options.beforeSendLog = (log) {
      if (log.level == SentryLogLevel.info) {
        // Filter out all info logs
        return null;
      }

      return log;
    };
  },
);

The beforeSend function receives a log object, and should return the log object if you want it to be sent to Sentry, or null if you want to discard it.

Instead of many thin logs that are hard to correlate, emit one comprehensive log per operation with all relevant context.

This makes debugging dramatically faster — one query returns everything about a specific order, user, or request.

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// ❌ Scattered thin logs
Sentry.logger.info('Starting checkout');
Sentry.logger.info('Validating cart');
Sentry.logger.info('Processing payment');
Sentry.logger.info('Checkout complete');

// ✅ One wide event with full context
Sentry.logger.info('Checkout completed', attributes: {
  'order_id': SentryLogAttribute.string(order.id),
  'user_id': SentryLogAttribute.string(user.id),
  'user_tier': SentryLogAttribute.string(user.subscription),
  'cart_value': SentryLogAttribute.double(cart.total),
  'item_count': SentryLogAttribute.int(cart.items.length),
  'payment_method': SentryLogAttribute.string('stripe'),
  'duration_ms': SentryLogAttribute.int(
      DateTime.now().difference(startTime).inMilliseconds),
});

Add attributes that help you prioritize and debug:

User context — tier, account age, lifetime value
Transaction data — order value, item count
Feature state — active feature flags
Request metadata — endpoint, method, duration

This lets you filter logs by high-value customers or specific features.

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Sentry.logger.info('API request completed', attributes: {
  // User context
  'user_id': SentryLogAttribute.string(user.id),
  'user_tier': SentryLogAttribute.string(user.plan),
  'account_age_days': SentryLogAttribute.int(user.ageDays),

  // Request data
  'endpoint': SentryLogAttribute.string('/api/orders'),
  'method': SentryLogAttribute.string('POST'),
  'duration_ms': SentryLogAttribute.int(234),

  // Business context
  'order_value': SentryLogAttribute.double(149.99),
});

Pick a naming convention and stick with it across your codebase. Inconsistent names make queries impossible.

Recommended: Use snake_case for custom attributes to match Dart conventions.

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// ❌ Inconsistent naming
{'user': SentryLogAttribute.string('123')}
{'userId': SentryLogAttribute.string('123')}
{'user_id': SentryLogAttribute.string('123')}
{'UserID': SentryLogAttribute.string('123')}

// ✅ Consistent snake_case
{
  'user_id': SentryLogAttribute.string('123'),
  'order_id': SentryLogAttribute.string('456'),
  'cart_value': SentryLogAttribute.double(99.99),
  'item_count': SentryLogAttribute.int(3),
}

The Dart SDK automatically sets several default attributes on all log entries to provide context and improve debugging:

environment: The environment set in the SDK if defined. This is sent from the SDK as sentry.environment.
release: The release set in the SDK if defined. This is sent from the SDK as sentry.release.
sdk.name: The name of the SDK that sent the log. This is sent from the SDK as sentry.sdk.name.
sdk.version: The version of the SDK that sent the log. This is sent from the SDK as sentry.sdk.version.

If the log was parameterized, Sentry adds the message template and parameters as log attributes.

message.template: The parameterized template string. This is sent from the SDK as sentry.message.template.
message.parameter.X: The parameters to fill the template string. X can either be the number that represent the parameter's position in the template string (sentry.message.parameter.0, sentry.message.parameter.1, etc) or the parameter's name (sentry.message.parameter.item_id, sentry.message.parameter.user_id, etc). This is sent from the SDK as sentry.message.parameter.X.

For example, with the following log:

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Sentry.logger.fmt.info("%s added %s to cart.", ["John", "Product 1"]);

Sentry will add the following attributes:

message.template: "%s added %s to cart."
message.parameter.0: "John"
message.parameter.1: "Product 1"

If user information is available in the current scope, the following attributes are added to the log:

user.id: The user ID.
user.name: The username.
user.email: The email address.

If a log is generated by an SDK integration, the SDK will set additional attributes to help you identify the source of the log.

origin: The origin of the log. This is sent from the SDK as sentry.origin.

Logs can get lost in certain crash scenarios, if the SDK can not send the logs before the app terminates. We are currently working on improving this to ensure that all logs are sent, at the latest on the next app restart.

Available integrations:

Dart Logging package

If there's an integration you would like to see, open a new issue on GitHub.

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