Essential Browser Extensions Every Developer Should Use

By Mason Goulding · Aug 7, 2025 Updated Aug 7, 2025

A curated, no-bloat toolbox to accelerate debugging, auditing, and shipping. Organize by use-case, keep performance budgets tight, and let extensions do the boring parts—so you can build.

How to Use This Guide (and Avoid Bloat)

Install by need, not by novelty. Keep a “dev” profile with these tools enabled and a separate, clean profile for real-world performance checks. Fewer extensions in your daily profile = more accurate Core Web Vitals.

Rule of 7: Cap active extensions to ~7 per profile; disable the rest until needed.
Session hygiene: Test in Incognito/Private with all extensions disabled before final QA.
Permissions: Prefer “on click” or “on specific sites.” Least privilege wins.

Framework DevTools (Component Introspection)

Extension	Use Case	Power Move
React Developer Tools	Inspect props/state, trace renders, Profiler for wasted updates.	Pair with Performance panel; record INP hotspots while profiling components.
Vue Devtools	Component tree, Vuex/Pinia stores, events timeline.	Time-travel store mutations to reproduce heisenbugs quickly.
Svelte Devtools	Reactive graph inspection, state snapshots.	Watch reactive chains to eliminate unnecessary invalidations.
Redux DevTools	Time-travel debugging, action diffs.	Export/import action traces to share minimal repros with teammates.

Accessibility Audits (Ship Inclusive by Default)

axe DevTools: Catch WCAG failures (names, roles, contrast) early. Export issue lists as tickets.
WAVE Evaluation Tool: Spot ARIA misuse and landmark gaps; great for quick layout semantics checks.
HeadingsMap: Visualize H1→H6 outline; fix hierarchy and anchor TOC mismatches fast.
Keyboard Navigator / Focus Indicator: Verify tab order and visible focus rings in minutes.

Pro tip: Run audits in both light/dark themes—contrast issues often hide in one.

Performance & Web Vitals (Reality Checks)

Web Vitals (by Google): Surface LCP, CLS, INP in-page while you interact. Great for regression sniff tests.
Requestly / ModHeader: Rewrite headers (CSP, cache), simulate slow networks, test canaries without server changes.
Performance-focused blockers (uBlock Origin): Temporarily block 3P scripts to quantify their real cost.
Cache Killer (toggle): Force fresh loads when debugging caching/CDN quirks.

Remember to test again with extensions off—lab numbers differ from field data.

APIs, Storage, and Data Readers

Postman Interceptor / Talend API Tester: Exercise endpoints from the browser; capture cookies/headers.
JSON Viewer: Pretty-print and collapse large JSON payloads; highlight invalid syntax.
Cookie Editor: Create/edit scoped cookies for auth/feature flag testing.
Local Storage Manager: Snapshot/restore localStorage/sessionStorage between test states.

Design & Front-End Finishing

WhatFont: Identify fonts, sizes, and line-height in one hover.
ColorZilla / Site Palette: Pickers + palette extraction; export to design systems.
Pesticide: Outline boxes to diagnose spacing and collapsing margins quickly.
CSS Peeper: Inspect computed styles, fonts, and assets without diving deep into DevTools.
Responsive Viewer / Window Resizer: Test multiple breakpoints side-by-side; screenshot variants.

Stack Intelligence & Fingerprinting

Wappalyzer / WhatRuns: Detect frameworks, analytics, CDNs. Useful for competitor teardowns.
User-Agent Switcher: Validate bot-specific responses and legacy fallbacks.

Security, Privacy & Compliance Helpers

uBlock Origin: Measure third-party cost deltas and test privacy-first modes.
Redirect Path: Visualize 301/302/JS redirects; spot chains and loops.
CSP Viewer: Inspect and test Content-Security-Policy headers live.
Cookie-Consent Debuggers: Validate consent state gating before tags fire.

My Minimalist Loadout (Daily Driver)

Keep this always on; enable the rest when needed:

React/Vue/Svelte Devtools (pick one)
axe DevTools
Web Vitals
Meta SEO Inspector
uBlock Origin
JSON Viewer
Wappalyzer

Extension Hygiene (Performance & Safety)

Scope permissions: Use “on click” or “on specific sites.” Avoid “read and change data on all sites.”
Pin + audit monthly: Unpin unused tools; remove anything unmaintained or noisy.
Profile isolation: Dev profile for extensions; clean profile for user-journey/perf tests.
Incognito discipline: Keep all extensions disabled in Incognito; enable one-by-one only when necessary.
Telemetry awareness: Some SEO/analytics extensions call home—review privacy policies.

Quick Checklist (Before You Ship)

✅ axe/WAVE clean: no critical a11y violations.
✅ Web Vitals acceptable: LCP ≤ 2.5s, CLS ≤ 0.05, INP ≤ 200ms (test with extensions off, too).
✅ Meta/OG/canonical correct (no duplicates; locale if applicable).
✅ Redirect Path shows no chains; canonical host enforced.
✅ CSP/HSTS visible; no mixed content.
✅ Links pass a crawl; no 4xx/5xx on key flows.

Key Takeaways

Extensions are accelerators—not crutches. Keep the loadout lean and intentional.
Use a dev profile with power tools, and a clean profile for real-world performance checks.
Automate audits where possible; verify final numbers with all extensions off.
Security and privacy aren’t optional—review permissions and headers every release.

Disclaimer: This guide is provided for educational and informational purposes only and does not constitute legal, financial, or professional advice. Content is offered “as-is” without warranties of any kind. Readers are solely responsible for implementation and must ensure compliance with applicable laws, licensing, and platform policies. Always apply the information only within authorized, ethical, and legal contexts.