sentry-browser-sdk

All Skills > SDK Setup > Browser SDK

Sentry Browser SDK

Opinionated wizard that scans your project and guides you through complete Sentry setup for browser JavaScript — vanilla JS, jQuery, static sites, WordPress, and any JS project without a framework-specific SDK.

Invoke This Skill When

• User asks to "add Sentry to a website" or set up Sentry for plain JavaScript
• User wants to install @sentry/browser or configure the Loader Script
• User has a WordPress, Shopify, Squarespace, or static HTML site
• User wants error monitoring, tracing, session replay, or logging without a framework
• No framework-specific SDK applies

Note: SDK versions and APIs below reflect @sentry/browser ≥10.0.0. Always verify against docs.sentry.io/platforms/javascript/ before implementing.

---

Phase 1: Detect

CRITICAL — Check for frameworks first. Framework-specific SDKs provide significantly better coverage and must be recommended before proceeding with @sentry/browser.

Step 1A: Framework Detection (Redirect If Found)

# Check for React
cat package.json 2>/dev/null | grep -E '"react"'

# Check for Next.js
cat package.json 2>/dev/null | grep '"next"'

# Check for Vue
cat package.json 2>/dev/null | grep '"vue"'

# Check for Angular
cat package.json 2>/dev/null | grep '"@angular/core"'

# Check for Svelte / SvelteKit
cat package.json 2>/dev/null | grep -E '"svelte"|"@sveltejs/kit"'

# Check for Remix
cat package.json 2>/dev/null | grep -E '"@remix-run/react"|"@remix-run/node"'

# Check for Nuxt
cat package.json 2>/dev/null | grep '"nuxt"'

# Check for Astro
cat package.json 2>/dev/null | grep '"astro"'

# Check for Ember
cat package.json 2>/dev/null | grep '"ember-source"'

# Check for Node.js server frameworks (wrong SDK entirely)
cat package.json 2>/dev/null | grep -E '"express"|"fastify"|"@nestjs/core"|"koa"'

If a framework is detected, stop and redirect:

Framework detected	Redirect to
next	Load sentry-nextjs-sdk skill — do not proceed here
react (without Next.js)	Load sentry-react-sdk skill — do not proceed here
vue	Suggest @sentry/vue — see docs.sentry.io/platforms/javascript/guides/vue/
@angular/core	Suggest @sentry/angular — see docs.sentry.io/platforms/javascript/guides/angular/
@sveltejs/kit	Load sentry-svelte-sdk skill — do not proceed here
svelte (SPA, no kit)	Suggest @sentry/svelte — see docs.sentry.io/platforms/javascript/guides/svelte/
@remix-run	Suggest @sentry/remix — see docs.sentry.io/platforms/javascript/guides/remix/
nuxt	Suggest @sentry/nuxt — see docs.sentry.io/platforms/javascript/guides/nuxt/
astro	Suggest @sentry/astro — see docs.sentry.io/platforms/javascript/guides/astro/
ember-source	Suggest @sentry/ember — see docs.sentry.io/platforms/javascript/guides/ember/
express / fastify / @nestjs/core	This is a Node.js server — load sentry-node-sdk or sentry-nestjs-sdk skill

Why redirect matters: Framework SDKs add router-aware transactions, error boundaries, component tracking, and often SSR coverage. Using @sentry/browser directly in a React or Next.js app loses all of that.

Only continue with @sentry/browser if no framework is detected.

Step 1B: Installation Method Detection

# Check if there's a package.json at all (bundler environment)
ls package.json 2>/dev/null

# Check package manager
ls package-lock.json yarn.lock pnpm-lock.yaml bun.lockb 2>/dev/null

# Check build tool
ls vite.config.ts vite.config.js webpack.config.js rollup.config.js esbuild.config.js 2>/dev/null
cat package.json 2>/dev/null | grep -E '"vite"|"webpack"|"rollup"|"esbuild"'

# Check for CMS or static site indicators
ls wp-config.php wp-content/ 2>/dev/null   # WordPress
ls _config.yml _config.yaml 2>/dev/null    # Jekyll
ls config.toml 2>/dev/null                 # Hugo
ls .eleventy.js 2>/dev/null                # Eleventy

# Check for existing Sentry
cat package.json 2>/dev/null | grep '"@sentry/'
grep -r "sentry-cdn.com\|js.sentry-cdn.com" . --include="*.html" -l 2>/dev/null | head -3

What to determine:

Question	Impact
package.json exists + bundler?	→ Path A: npm install
WordPress, Shopify, static HTML, no npm?	→ Path B: Loader Script
Script tags only, no Loader Script access?	→ Path C: CDN bundle
Already has @sentry/browser?	Skip install, go straight to feature config
Build tool is Vite / webpack / Rollup / esbuild?	Source maps plugin to configure

---

Phase 2: Recommend

Present a recommendation based on what you found. Lead with a concrete proposal, don't ask open-ended questions.

Recommended (core coverage):

• ✅ Error Monitoring — always; captures unhandled errors and promise rejections
• ✅ Tracing — recommended for any interactive site; tracks page load and user interactions
• ✅ Session Replay — recommended for user-facing apps; records sessions around errors

Optional (enhanced observability):

• ⚡ User Feedback — capture reports directly from users after errors
• ⚡ Logging — structured logs via Sentry.logger.*; requires npm or CDN logs bundle (not available via Loader Script)
• ⚡ Profiling — JS Self-Profiling API; beta, Chromium-only, requires Document-Policy: js-profiling response header

Feature recommendation logic:

Feature	Recommend when...
Error Monitoring	Always — non-negotiable baseline
Tracing	Always for interactive pages — page load + navigation spans are high-value
Session Replay	User-facing app, support flows, or checkout pages
User Feedback	Support-focused app; want in-app bug reports with screenshots
Logging	Structured log search or log-to-trace correlation needed; npm path only
Profiling	Performance-critical, Chromium-only app; Document-Policy: js-profiling header required

Installation path recommendation:

Scenario	Recommended path
Project has package.json + bundler	Path A (npm) — full features, source maps, tree-shaking
WordPress, Shopify, Squarespace, static HTML	Path B (Loader Script) — zero build tooling, always up to date
Static HTML without Loader Script access	Path C (CDN bundle) — manual <script> tag

Propose: "I recommend setting up Error Monitoring + Tracing + Session Replay using Path A (npm). Want me to also add Logging or User Feedback?"

---

Phase 3: Guide

Path A: npm / yarn / pnpm (Recommended — Bundler Projects)

Install

npm install @sentry/browser --save
# or
yarn add @sentry/browser
# or
pnpm add @sentry/browser

Create src/instrument.ts

Sentry must initialize before any other code runs. Put Sentry.init() in a dedicated sidecar file:

import * as Sentry from "@sentry/browser";

Sentry.init({
  dsn: import.meta.env.VITE_SENTRY_DSN, // Adjust per build tool (see table below)
  environment: import.meta.env.MODE,
  release: import.meta.env.VITE_APP_VERSION, // inject at build time

  sendDefaultPii: true,

  integrations: [
    Sentry.browserTracingIntegration(),
    Sentry.replayIntegration({
      maskAllText: true,
      blockAllMedia: true,
    }),
  ],

  // Tracing
  tracesSampleRate: 1.0, // lower to 0.1–0.2 in production
  tracePropagationTargets: ["localhost", /^https:\/\/yourapi\.io/],

  // Session Replay
  replaysSessionSampleRate: 0.1,
  replaysOnErrorSampleRate: 1.0,

  enableLogs: true,
});

DSN environment variable by build tool:

Build Tool	Variable Name	Access in code
Vite	VITE_SENTRY_DSN	import.meta.env.VITE_SENTRY_DSN
Custom webpack	SENTRY_DSN	process.env.SENTRY_DSN
esbuild	SENTRY_DSN	process.env.SENTRY_DSN
Rollup	SENTRY_DSN	process.env.SENTRY_DSN

Entry Point Setup

Import instrument.ts as the very first import in your entry file:

// src/main.ts or src/index.ts
import "./instrument";  // ← MUST be first

// ... rest of your app

Source Maps Setup (Strongly Recommended)

Without source maps, stack traces show minified code. Set up the build plugin to upload source maps automatically:

No dedicated browser wizard: There is no npx @sentry/wizard -i browser flag. The closest is npx @sentry/wizard@latest -i sourcemaps which configures source map upload only for an already-initialized SDK.

Vite (vite.config.ts):

import { defineConfig } from "vite";
import { sentryVitePlugin } from "@sentry/vite-plugin";

export default defineConfig({
  build: { sourcemap: "hidden" },
  plugins: [
    // sentryVitePlugin MUST be last
    sentryVitePlugin({
      org: process.env.SENTRY_ORG,
      project: process.env.SENTRY_PROJECT,
      authToken: process.env.SENTRY_AUTH_TOKEN,
    }),
  ],
});

webpack (webpack.config.js):

const { sentryWebpackPlugin } = require("@sentry/webpack-plugin");

module.exports = {
  devtool: "hidden-source-map",
  plugins: [
    sentryWebpackPlugin({
      org: process.env.SENTRY_ORG,
      project: process.env.SENTRY_PROJECT,
      authToken: process.env.SENTRY_AUTH_TOKEN,
    }),
  ],
};

Rollup (rollup.config.js):

import { sentryRollupPlugin } from "@sentry/rollup-plugin";

export default {
  output: { sourcemap: "hidden" },
  plugins: [
    sentryRollupPlugin({
      org: process.env.SENTRY_ORG,
      project: process.env.SENTRY_PROJECT,
      authToken: process.env.SENTRY_AUTH_TOKEN,
    }),
  ],
};

esbuild (build.js):

const { sentryEsbuildPlugin } = require("@sentry/esbuild-plugin");

require("esbuild").build({
  entryPoints: ["src/index.ts"],
  bundle: true,
  sourcemap: "hidden",
  plugins: [
    sentryEsbuildPlugin({
      org: process.env.SENTRY_ORG,
      project: process.env.SENTRY_PROJECT,
      authToken: process.env.SENTRY_AUTH_TOKEN,
    }),
  ],
});

⚠️ esbuild plugin does not fully support splitting: true. Use sentry-cli instead if code splitting is enabled.

Using sentry-cli (any toolchain / CI):

# After your build step:
npx @sentry/cli sourcemaps inject ./dist
npx @sentry/cli sourcemaps upload ./dist

Add .env for auth (never commit):

SENTRY_AUTH_TOKEN=sntrys_...
SENTRY_ORG=my-org-slug
SENTRY_PROJECT=my-project-slug

---

Path B: Loader Script (WordPress, Static Sites, Shopify, Squarespace)

Best for: Sites without a build system. The Loader Script is a single <script> tag that lazily loads the full SDK, always stays up to date via Sentry's CDN, and buffers errors before the SDK loads.

Get the Loader Script: Sentry UI → Settings → Projects → (your project) → SDK Setup → Loader Script

Copy the generated tag and place it as the first script on every page:

<!DOCTYPE html>
<html>
  <head>
    <!-- Configure BEFORE the loader tag -->
    <script>
      window.sentryOnLoad = function () {
        Sentry.init({
          // DSN is already configured in the loader URL
          tracesSampleRate: 1.0,
          replaysSessionSampleRate: 0.1,
          replaysOnErrorSampleRate: 1.0,
        });
      };
    </script>

    <!-- Loader Script FIRST — before all other scripts -->
    <script
      src="https://js.sentry-cdn.com/YOUR_PUBLIC_KEY.min.js"
      crossorigin="anonymous"
    ></script>
  </head>
  ...
</html>

Loader loading modes:

Mode	How	When SDK loads
Lazy (default)	Nothing extra	On first error or manual Sentry call
Eager	Add data-lazy="no" to <script>	After all page scripts finish
Manual	Call Sentry.forceLoad()	Whenever you call it

Safe to call before SDK loads (buffered):

• Sentry.captureException()
• Sentry.captureMessage()
• Sentry.captureEvent()
• Sentry.addBreadcrumb()
• Sentry.withScope()

For other methods, use Sentry.onLoad():

<script>
  window.Sentry && Sentry.onLoad(function () {
    Sentry.setUser({ id: "123" });
  });
</script>

Set release via global (optional):

<script>
  window.SENTRY_RELEASE = { id: "my-app@1.0.0" };
</script>

Loader Script limitations:

• ❌ No Sentry.logger.* (logging) — npm path only
• ❌ No framework-specific features (React ErrorBoundary, Vue Router tracking, etc.)
• ❌ Tracing headers only added to fetch calls made after SDK loads
• ❌ Version changes take a few minutes to propagate via CDN cache
• ⚠️ Use defer (not async) on all other scripts when using the loader

CSP requirements:

script-src: https://browser.sentry-cdn.com https://js.sentry-cdn.com
connect-src: *.sentry.io

---

Path C: CDN Bundles (Manual Script Tags)

Best for: Pages that can't use the Loader Script but need synchronous loading.

Pick the bundle that matches your feature needs and place it before all other scripts:

Errors only (minimal footprint):

<script
  src="https://browser.sentry-cdn.com/10.42.0/bundle.min.js"
  integrity="sha384-L/HYBH2QCeLyXhcZ0hPTxWMnyMJburPJyVoBmRk4OoilqrOWq5kU4PNTLFYrCYPr"
  crossorigin="anonymous"
></script>

Errors + Tracing:

<script
  src="https://browser.sentry-cdn.com/10.42.0/bundle.tracing.min.js"
  integrity="sha384-DIqcfVcfIewrWiNWfVZcGWExO5v673hkkC5ixJnmAprAfJajpUDEAL35QgkOB5gw"
  crossorigin="anonymous"
></script>

Errors + Session Replay:

<script
  src="https://browser.sentry-cdn.com/10.42.0/bundle.replay.min.js"
  integrity="sha384-sbojwIJFpv9duIzsI9FRm87g7pB15s4QwJS1m1xMSOdV1CF3pwgrPPEu38Em7M9+"
  crossorigin="anonymous"
></script>

Errors + Tracing + Replay (recommended full setup):

<script
  src="https://browser.sentry-cdn.com/10.42.0/bundle.tracing.replay.min.js"
  integrity="sha384-oo2U4zsTxaHSPXJEnXtaQPeS4Z/qbTqoBL9xFgGxvjJHKQjIrB+VRlu97/iXBtzw"
  crossorigin="anonymous"
></script>

Errors + Tracing + Replay + User Feedback:

<script
  src="https://browser.sentry-cdn.com/10.42.0/bundle.tracing.replay.feedback.min.js"
  integrity="sha384-SmHU39Qs9cua0KLtq3A6gis1/cqM1nZ6fnGzlvWAPiwhBDO5SmwFQV65BBpJnB3n"
  crossorigin="anonymous"
></script>

Full bundle (all features):

<script
  src="https://browser.sentry-cdn.com/10.42.0/bundle.tracing.replay.feedback.logs.metrics.min.js"
  integrity="sha384-gOjSzRxwpXpy0FlT6lg/AVhagqrsUrOWUO7jm6TJwuZ9YVHtYK0MBA2hW2FGrIGl"
  crossorigin="anonymous"
></script>

CDN bundle variants summary:

Bundle	Features	When to use
bundle.min.js	Errors only	Absolute minimum footprint
bundle.tracing.min.js	+ Tracing	Performance monitoring
bundle.replay.min.js	+ Replay	Session recording
bundle.tracing.replay.min.js	+ Tracing + Replay	Full observability
bundle.tracing.replay.feedback.min.js	+ User Feedback	+ in-app feedback widget
bundle.logs.metrics.min.js	+ Logs + Metrics	Structured logs (CDN)
bundle.tracing.replay.feedback.logs.metrics.min.js	Everything	Max coverage

Initialize after the script tag:

<script>
  Sentry.init({
    dsn: "https://YOUR_KEY@o0.ingest.sentry.io/YOUR_PROJECT",
    environment: "production",
    release: "my-app@1.0.0",
    integrations: [
      Sentry.browserTracingIntegration(),
      Sentry.replayIntegration({
        maskAllText: true,
        blockAllMedia: true,
      }),
    ],
    tracesSampleRate: 1.0,
    tracePropagationTargets: ["localhost", /^https:\/\/yourapi\.io/],
    replaysSessionSampleRate: 0.1,
    replaysOnErrorSampleRate: 1.0,
  });
</script>

CDN CSP requirements:

script-src: https://browser.sentry-cdn.com https://js.sentry-cdn.com
connect-src: *.sentry.io

---

For Each Agreed Feature

Walk through features one at a time. Load the reference file, follow its steps, verify before moving on:

Feature	Reference	Load when...
Error Monitoring	${SKILL_ROOT}/references/error-monitoring.md	Always (baseline)
Tracing	${SKILL_ROOT}/references/tracing.md	Page load / API call tracing
Session Replay	${SKILL_ROOT}/references/session-replay.md	User-facing app
Logging	${SKILL_ROOT}/references/logging.md	Structured log search; npm or CDN logs bundle (not Loader Script)
Profiling	${SKILL_ROOT}/references/profiling.md	Performance-critical, Chromium-only
User Feedback	${SKILL_ROOT}/references/user-feedback.md	Capture user reports after errors

For each feature: Read ${SKILL_ROOT}/references/<feature>.md, follow steps exactly, verify it works.

---

Configuration Reference

Key Sentry.init() Options

Option	Type	Default	Notes
dsn	string	—	Required. SDK disabled when empty
environment	string	"production"	e.g., "staging", "development"
release	string	—	e.g., "my-app@1.0.0" or git SHA — links errors to releases
sendDefaultPii	boolean	false	Includes IP addresses and request headers
tracesSampleRate	number	—	0–1; 1.0 in dev, 0.1–0.2 in prod
tracesSampler	function	—	Per-transaction sampling; overrides rate
tracePropagationTargets	(string|RegExp)[]	same-origin	Outgoing URLs that receive distributed tracing headers
replaysSessionSampleRate	number	—	Fraction of all sessions recorded
replaysOnErrorSampleRate	number	—	Fraction of error sessions recorded
enableLogs	boolean	false	Enable Sentry.logger.* API (npm or CDN logs bundle; not Loader Script)
attachStackTrace	boolean	false	Stack traces on captureMessage() calls
maxBreadcrumbs	number	100	Breadcrumbs stored per event
debug	boolean	false	Verbose SDK output to console
tunnel	string	—	Proxy URL to bypass ad blockers
ignoreErrors	(string|RegExp)[]	[]	Drop errors matching these patterns
denyUrls	(string|RegExp)[]	[]	Drop errors from scripts at these URLs
allowUrls	(string|RegExp)[]	[]	Only capture errors from these script URLs
spotlight	boolean|string	false	Forward events to Spotlight local dev overlay

Browser-Specific Options

Option	Type	Default	Notes
cdnBaseUrl	string	—	Base URL for lazy-loading integrations
skipBrowserExtensionCheck	boolean	false	Skip check for browser extension context

window.SENTRY_RELEASE Global (CDN / Loader Path)

Set the release version before the SDK loads:

<script>
  window.SENTRY_RELEASE = { id: "my-app@1.0.0" };
</script>

---

Verification

Trigger test events to confirm Sentry is receiving data:

npm / CDN path:

<!-- Add temporarily to your page -->
<button onclick="throw new Error('Sentry Browser Test Error')">
  Test Error
</button>

Performance verification (npm path):

import * as Sentry from "@sentry/browser";

Sentry.startSpan({ name: "Test Span", op: "test" }, () => {
  // your operation
});

Manual capture:

Sentry.captureException(new Error("Manual test"));
Sentry.captureMessage("Manual test message", "info");

Check the Sentry dashboard:

• Issues → error appears within seconds
• Traces → page load transaction visible
• Replays → session recording visible after page interaction
• Logs → structured log entries if logging enabled (npm or CDN logs bundle)

Set debug: true in Sentry.init() and check the browser console if nothing appears.

---

Phase 4: Cross-Link

After completing browser setup, check for a companion backend missing Sentry coverage:

ls ../backend ../server ../api ../go ../python 2>/dev/null
cat ../go.mod 2>/dev/null | head -3
cat ../requirements.txt ../pyproject.toml 2>/dev/null | head -3
cat ../Gemfile 2>/dev/null | head -3
cat ../pom.xml 2>/dev/null | grep '<artifactId>' | head -3
cat ../composer.json 2>/dev/null | head -3

If a backend exists without Sentry configured, suggest the matching skill:

Backend detected	Suggest skill
Go (go.mod)	sentry-go-sdk
Python (requirements.txt, pyproject.toml)	sentry-python-sdk
Ruby (Gemfile)	sentry-ruby-sdk
PHP (composer.json)	sentry-php-sdk
.NET (*.csproj, *.sln)	sentry-dotnet-sdk
Java (pom.xml, build.gradle)	See docs.sentry.io/platforms/java/
Node.js (Express, Fastify)	sentry-node-sdk
NestJS (@nestjs/core)	sentry-nestjs-sdk

---

Troubleshooting

Issue	Solution
Events not appearing	Set debug: true, check DSN, open browser console for SDK errors
Source maps not working	Build in production mode (npm run build); verify SENTRY_AUTH_TOKEN is set
Minified stack traces	Source maps not uploading — check build plugin config; run npx @sentry/wizard@latest -i sourcemaps
CDN bundle not found	Check version number in URL; see browser.sentry-cdn.com for latest
SRI integrity error	Hash mismatch — re-copy the full <script> tag including integrity attribute from this skill
Loader Script not firing	Verify it's the first <script> on the page; check for CSP errors in console
Tracing not working with Loader	Fetch calls before SDK loads won't be traced — wrap early calls in Sentry.onLoad()
sentryOnLoad not called	Must define window.sentryOnLoad before the loader <script> tag
Logging not available	Sentry.logger.* requires npm or a CDN bundle with .logs. in its name — not supported via Loader Script
Profiling not working	Verify Document-Policy: js-profiling header on document responses; Chromium-only
Ad blockers dropping events	Set tunnel: "/sentry-tunnel" and add a server-side relay endpoint
Session replay not recording	Confirm replayIntegration() is in init; check replaysSessionSampleRate > 0
Replay CSP errors	Add worker-src 'self' blob: and child-src 'self' blob: to your CSP
tracePropagationTargets not matching	Check regex escaping; default is same-origin only
Events blocked by browser extension	Add denyUrls: [/chrome-extension:\/\//] to filter extension errors
High event volume	Lower sampleRate (errors) and tracesSampleRate from 1.0 in production
Source maps uploaded after deploy	Source maps must be uploaded before errors occur — integrate into CI/CD
esbuild splitting conflict	sentryEsbuildPlugin doesn't support splitting: true — use sentry-cli instead