Data lookups

Fast, reliable data lookups

Dependable answers, just a few clicks away — free for everyone, no account needed.

Web & internet

DNS record types
A, AAAA, CNAME, MX, TXT, DKIM, DMARC and friends explained.
Email error codes
What SMTP 421, 550 and 554 are telling you, and what to do about it.
HTTP headers
The purpose and syntax of common request and response headers.
HTTP status codes
What 404, 429, 502 and every other HTTP response code actually mean.
MIME types
The correct content type for PDFs, JSON, images, audio and video.
Network port numbers
Which port HTTPS, SSH, SMTP, DNS and the rest listen on.

Code & characters

ASCII table
All 128 ASCII codes in decimal, hex, octal and binary.
CSS colour names
Every named CSS colour with its hex and RGB values.
HTML entities
Codes for copyright, arrows, quotes, maths and other symbols.
Keyboard key codes
JavaScript key values, codes and the legacy keyCode numbers.
Unicode characters
Symbol, code point, HTML entity and UTF-8 bytes for useful characters.

Developer reference

Command-line reference
Common CMD, PowerShell, Linux and Git commands and what they do.
Date-format codes
Date and time tokens for PHP, JavaScript, Python and Excel.
File extensions
What opens .heic, .webp, .svg, .eps and hundreds of other files.
Regular-expression reference
Regex tokens, character classes, flags and worked examples.
SQL data types
Types side by side across MySQL, SQL Server and PostgreSQL.

Countries & standards

Country calling codes
The international dialling prefix for any country.
Country information
Capitals, currencies, regions and key facts for countries worldwide.
Currency codes
GBP, USD, EUR and other ISO 4217 currency identifiers.
ISO country codes
Alpha-2, alpha-3 and numeric ISO 3166 codes.
Language codes
ISO 639 language codes and the HTML lang tags that use them.
Postcode formats
Every valid postcode or ZIP pattern by country — the UK alone has six.
UK postcode areas
Which town or region each UK postcode prefix covers.
VAT & tax ID formats
The shape of VAT and business tax numbers by country.

Sizes & measurements

Image dimensions
Recommended image sizes for common web and social uses.
Measurement conversions
Length, weight, volume, pressure and temperature conversions.
Paper sizes
A4, Letter, Legal and envelope dimensions in mm and inches.
Roman numerals
Convert a number to Roman numerals, or a numeral back to a number.
Screen resolutions
Common display and video dimensions, from VGA to 8K.

Science & engineering

Chemical elements
All 118 elements with symbol, atomic number and basic properties.
Electrical wire sizes
AWG diameter, cross-section and approximate current capacity.
Resistor colour codes
Read resistance and tolerance from the colour bands.

Everyday

Vehicle warning lights
What that symbol on your dashboard means — and how urgent it is.

This site

Reverse business lookup
Search our directory by phone number, website or address.