Browser & Device Diagnostics — IP, Screen Resolution & Luhn Validator

Device & Browser Intelligence: Public IP, Screen Resolution, and Luhn Validation

Every time your browser connects to the web, your hardware environment broadcasts specific technical parameters to servers and websites. What is your external public IP address? What is your exact display screen resolution and device pixel ratio for responsive web testing? Is a credit card number mathematically valid according to the ISO 7812 standard? Explore our free browser and device diagnostics below.

Understanding Client-Side Browser Fingerprinting & Telemetry

When you visit a website, your web client interacts with servers through multiple software and hardware layers:

The Network Layer (IP Address): Your router's public IP assigned by your ISP. This identifies your general geographic location and routing path across the global Internet.
The Display & Viewport Layer (CSS Pixels vs. Physical Pixels): High-DPI screens (Apple Retina, 4K displays) render at 2x or 3x device pixel ratios (DPR), meaning a CSS viewport of 390px × 844px on an iPhone actually displays on a physical 1170px × 2532px OLED screen!
Payment Validation (The Luhn Algorithm): Created by IBM scientist Hans Peter Luhn in 1954, the Luhn formula (also known as the "MOD 10" algorithm) validates credit card numbers, IMEI phone serials, and national identification numbers against accidental input typos before charging payment gateways.

Payment Card Brand	Major Industry Identifier (MII) Prefix	Standard Digit Length	Validation Algorithm
Visa	Starts with 4	13 or 16 digits	Luhn MOD 10 Checksum
MasterCard	Starts with 51–55 or 2221–2720	16 digits	Luhn MOD 10 Checksum
American Express (Amex)	Starts with 34 or 37	15 digits	Luhn MOD 10 Checksum
Discover	Starts with 6011, 622126–622925, 644–649, 65	16 digits	Luhn MOD 10 Checksum

Tool-by-Tool Guide to Browser & Device Tools

1. What Is My IP: Instant Public Connection Details

The What Is My Ip tool queries server handshake sockets to reveal:

Public IPv4 and IPv6: Your outward-facing internet address (different from local router IPs like 192.168.1.1).
ISP & Hostname: The telecommunications carrier providing your fiber, cable, or mobile 5G internet.
Approximate Geolocation: City, state, country, and timezone.

2. What Is My Screen Resolution: Responsive Web Design Testing

Web developers and graphic designers frequently need to confirm display specifications. The What Is My Screen Resolution tool reads JavaScript screen properties in real time:

Physical Monitor Dimensions (e.g., 1920 × 1080 or 2560 × 1440).
Current Browser Viewport Window (width and height excluding operating system taskbars).
Device Pixel Ratio (DPR) for Retina scaling and high-resolution asset testing.
Color Bit Depth (24-bit True Color vs 30-bit HDR).

3. Credit Card Validator: Mathematical Luhn Checksum Verification

The Credit Card Validator tests whether a credit or debit card number is mathematically authentic using the Luhn algorithm. It verifies card issuer prefixes, digit length, and checksum calculations entirely in your browser—zero card numbers are ever sent over the network or saved, making it safe for developer payment checkout testing.

Frequently Asked Questions

Is it safe to test my credit card number on the Credit Card Validator?

Yes. The validation happens 100% locally on your computer inside your browser using client-side JavaScript. The tool does not store, transmit, or process financial payments; it solely verifies that the number satisfies the mathematical Luhn checksum equation.

What is the difference between screen resolution and viewport size?

Screen resolution is the total physical pixel count of your monitor hardware (e.g., 1920×1080). Viewport size is the actual available pixel area inside your browser window where web content renders, which is smaller due to toolbars, address bars, and OS window frames.

Why does my public IP address change periodically?

Most residential Internet Service Providers (ISPs) assign dynamic IP addresses that change whenever your router reboots or after a set lease time expires. Only business accounts typically pay for fixed static IP addresses.

How does the Luhn algorithm detect typos?

The Luhn formula doubles every second digit from right to left, sums the individual digits, and checks if the total modulo 10 is zero. This mathematical parity check catches virtually all single-digit entry errors and adjacent digit transpositions.