Functional Software

Overview

Functional Software, Inc. is the legal entity behind Sentry — one of the most widely deployed application error monitoring and performance observability platforms in software development. Engineering teams at companies of all sizes integrate the Sentry SDK into their web applications, mobile apps, and backend services to capture unhandled exceptions, track performance regressions, and diagnose production bugs before users report them.

On websites and web applications, the Sentry Browser SDK (@sentry/browser or @sentry/nextjs, loaded from browser.sentry-cdn.com or bundled directly) instruments the JavaScript runtime to intercept errors and performance data. The collected data is purely diagnostic — it serves application engineering, not marketing or advertising.

What This Script Does

The Sentry Browser SDK instruments the web application runtime for error and performance monitoring:

Exception capture: The SDK hooks into the browser's global window.onerror handler and window.addEventListener('unhandledrejection') to intercept all uncaught JavaScript exceptions and unhandled Promise rejections. For each error, Sentry captures: the error message and type, a parsed stack trace with source-mapped file names and line numbers, the browser user agent string, OS and device metadata, and the URL where the error occurred.

Breadcrumb collection: In the background, Sentry automatically records a breadcrumb trail of recent events leading up to each error — previous page navigations, XHR/fetch network requests (URL, method, status code), console log calls, and UI click interactions. These breadcrumbs provide developers context about what the user was doing before the error occurred. Breadcrumbs are captured in memory and only transmitted when an error event is sent.

Performance monitoring (Sentry Performance): When performance monitoring is enabled, the SDK creates transaction spans that measure page load timing (using the Navigation Timing API), resource loading durations, XHR/fetch latency, and custom instrumented operations. These performance traces are sent to Sentry alongside error events.

Session tracking: Sentry uses short-lived session identifiers (stored in sessionStorage, not persistent cookies) to correlate errors within a single user session and report session-level crash rates. These session identifiers are not used for marketing profiling and do not persist beyond the browser tab session.

User context (optional, explicitly configured): If the implementing application explicitly calls Sentry.setUser({ id, email, username }), Sentry attaches that user context to error reports. This is an optional, developer-configured feature — Sentry does not autonomously collect user identity information. Applications handling sensitive data should use Sentry's PII scrubbing features to strip personal data before transmission.

Data transmission: Error and performance events are sent to sentry.io (or a self-hosted Sentry instance) via the Fetch API. The Sentry DSN (Data Source Name) in the script configuration determines the destination project.

Consent & Compliance

Sentry is a functional application reliability tool:

• GDPR: Sentry collects technical diagnostic data — stack traces, browser metadata, breadcrumbs, performance timing. This constitutes personal data under GDPR when it includes IP addresses or explicitly configured user identifiers. The lawful basis is typically legitimate interests (Article 6(1)(f)) — maintaining application reliability and diagnosing defects that directly impact users is a legitimate interest that does not require consent. Sentry provides GDPR-aligned DPA terms and offers data residency options (EU-based ingestion at de.sentry.io).
• ePrivacy Directive: Sentry uses sessionStorage for session correlation — not persistent cookies. The ePrivacy Directive's consent requirement applies to persistent cookies and similar tracking technologies. Short-lived sessionStorage used for error correlation within a single tab session is generally considered strictly necessary for application reliability and does not require consent.
• CCPA: Sentry acts as a service provider processing technical diagnostic data on behalf of the application operator. Error diagnostic data is not used for advertising or sold to third parties.
• PII scrubbing: Sentry supports server-side and client-side scrubbing of personal data from error payloads. Applications processing sensitive data (healthcare, finance) should configure appropriate scrubbing rules.

Should You Block This Without Consent?

No. Sentry is a functional application error monitoring tool that directly supports site reliability. It does not track users for marketing purposes, does not set persistent tracking cookies, and collects only technical diagnostic data. It can load as a functional script without requiring analytics or marketing consent.