Learn more about what Sentry uses to create a trail of events (breadcrumbs) that happened prior to an issue.

Sentry uses breadcrumbs to create a trail of events that happened prior to an issue. These events are very similar to traditional logs, but can record more rich structured data.

This page provides an overview of manual breadcrumb recording and customization. Learn more about the information that displays on the Issue Details page and how you can filter breadcrumbs to quickly resolve issues in Using Breadcrumbs.

You can manually add breadcrumbs whenever something interesting happens. For example, you might manually record a breadcrumb if the user authenticates or another state change occurs.

Manually record a breadcrumb:

crumb =
  category: "auth",
  message: "Authenticated user #{}",
  level: "info"

Appropriate places to inject Breadcrumbs may be places like your HTTP library:

# Instrumenting Faraday with a middleware:

class SentryFaradayMiddleware
  def call
    # Add a breadcrumb every time we complete an HTTP request do |response_env|
      crumb =
        data: { response_env: response_env },
        category: "faraday",
        message: "Completed request to #{request_env[:url]}"

The available breadcrumb keys are type, category, message, level, timestamp (which many SDKs will set automatically for you), and data, which is the place to put any additional information you'd like the breadcrumb to include. Using keys other than these six won't cause an error, but will result in the data being dropped when the event is processed by Sentry.

SDKs and their associated integrations will automatically record many types of breadcrumbs. For example, the browser JavaScript SDK will automatically record clicks and key presses on DOM elements, XHR/fetch requests, console API calls, and all location changes.

SDKs allow you to customize breadcrumbs through the before_breadcrumb hook.

This hook is passed an already assembled breadcrumb and, in some SDKs, an optional hint. The function can modify the breadcrumb or decide to discard it entirely by returning null:

Sentry.init do |config|
  # ...

  # this will be called before every breadcrumb is added to the breadcrumb buffer
  # you can use it to
  # - remove the data you don't want to send
  # - add additional info to the data
  config.before_breadcrumb = lambda do |breadcrumb, hint|
    breadcrumb.message = "foo"

For information about what can be done with the hint, see Filtering Events.

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