Why does the OS shown look different from my actual OS?

Modern browsers freeze the User-Agent's OS portion as a privacy measure — Chrome and Firefox report a generic Windows 10 or macOS 10.15 even on newer versions. The Sec-CH-UA-Platform-Version header has the accurate value if the site requests it.

Is hardwareConcurrency the actual CPU count?

It's the number of logical processors the browser is willing to report. Some browsers cap it for fingerprinting resistance — typically maxes at 16 even on high-core systems.

How do I detect mobile vs desktop?

Don't rely on navigator.userAgent — use feature detection. matchMedia('(pointer: coarse)') tells you if the primary input is touch. matchMedia('(max-width: 768px)') tells you the viewport width. Together they cover most real cases.

navigator · screen · viewport · features · live

Inspect your browser at a glance

Q: Is anything sent to a server?

No — all reads are local browser APIs.

Read navigator, screen, viewport and feature-detection flags. Everything is pulled from your live browser — nothing leaves the page.

Browser Info

Features

0/0

supported

Cores

—

logical

Viewport

—

DPR

—

ratio

input · user-agent

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output · environment

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Quick Start

How to read browser info

The data is pulled from navigator, screen, window and Intl. Read it, copy it, compare with what you expected.

01
Read the UA
The full User-Agent string is at the top. Copy it for bug reports.
Lookups reference the IANA registries (MIME, HTTP status, TLDs) bundled at build time — no live network calls, no rate limits, no leaked queries.
uaIANAregistryofflinelive
ua · querystring · IANA
```
Mozilla/5.0 ...
```
loaded · IANA bundlespec · ready
02
Check the environment
Cores, memory, language and timezone come from navigator + Intl.
Builders emit canonical syntax per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs) so the output passes spec-compliant parsers.
envRFC 9110canonicalspec-compliantlive
env · optionsok · live
```
cores=8 dpr=2
```
options applied · livecanonical
03
Verify feature support
21 commonly-used APIs are feature-detected.
Validation flags common pitfalls — uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8 — before they bite production.
featurevalidationlintpitfallslive
features · looked upsupported · ready
```
WebGPU: yes
```
result · livevalidated
04
Copy a report
One click grabs UA + cards + feature list as plain text.
Copy writes the snippet directly into your clipboard; downloads emit the right extension and MIME so curl/httpie pick them up correctly.
copyclipboardMIME-correctblobcurl-ready
ok · copiedready · done
```
Copied report
```
shipped · ready to shipsuccess

Pro tips

Web-spec details that bite later

Idempotency saves retries

POST/PUT/DELETE should be safely retried. Use idempotency keys and return the same response on duplicate requests.

Match RFC 9110 status codes

Don’t invent codes. 422 for validation errors, 409 for conflicts, 429 for rate limits. Standard codes work with off-the-shelf clients.

Set <code>Cache-Control</code> deliberately

Default browser caching is conservative. Use max-age + stale-while-revalidate for hot endpoints.

Validate Open Graph in dev

OG tags break silently. Use a previewer like OG Generator + Facebook’s debugger before launch.

CORS is a server concern

The browser sends the preflight; the server decides. Wildcard origins disable credentials — be explicit.

MIME drives behaviour

Servers must send the right Content-Type. Browsers sniff but the spec says they shouldn’t — be explicit to avoid surprises.

Use Cases

When to inspect the browser

Bug triage, feature gating, telemetry.

Bug triage

Paste the full report into a ticket for repro context. Bundled from IANA registries at build time — no live network call, no rate limit, no leaked queries. The MIME, TLD, and status-code tables are baked in so the tool works offline once loaded.

spec-compliant

Feature gating

Verify a feature you assume exists is actually there. Output is canonical per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs), so spec-compliant parsers accept it as-is. Cross-browser and cross-library behaviour stays consistent.

offline

Telemetry sanity

Confirm your analytics sees the same UA / DPR. Pairs with the curl-to-fetch converter for end-to-end test stubs — copy the curl from DevTools, paste, get an idiomatic fetch() body. Drop into Playwright/Vitest fixtures without manual translation.

IANA-backed

Cross-device QA

Spot-check screen/viewport on each device. Catches common pitfalls (uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8) before they bite production. Validation flags rather than auto-corrects so you stay in control.

RFC-aligned

Onboarding checks

See if a new dev's setup has all the right APIs. Validation runs as you type — copy only when the output is shaped correctly. The output drops directly into nginx, Apache, or CDN configs without re-formatting or re-quoting.

production-grade

Customer help

Walk a user through gathering their browser details. Same input plus same options always produces identical canonical output, so the tool is safe to embed in CI scripts that diff against expected configs.

curl-ready

FAQ

Frequently asked questions

Is the UA reliable?

It's what your browser sends. Browsers may freeze parts of it (UA reduction).

Why is some data missing?

Some fields (deviceMemory, vendor) are not exposed in all browsers.

Is anything sent to a server?

No — the page reads only your local browser APIs.

What about Client Hints?

Not shown here — Client Hints are surfaced via HTTP headers, not navigator.

How do I read feature support elsewhere?

Use the corresponding API (e.g. <code>'serviceWorker' in navigator</code>) at runtime.

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