Breadcrumbs appends a short history of events to crash reports. These help to diagnose the cause of the attached crash by providing context around when it happened.

Breadcrumb events include:

• user-triggered actions listed in tools/metrics/actions.xml
• per-tab actions, e.g., when navigation starts/finishes
• per-browser actions, e.g., number of tabs opened/closed/moved
• memory pressure
• startup/shutdown

Breadcrumbs are not uploaded or stored on disk unless the user has consented to metrics reporting.