Reference & Cheatsheets
427 free reference & cheatsheets tools in the Developer Tools collection — every one runs in your browser with no signup and no uploads. Page 2 of 5.
World Deserts Reference
The 20 largest deserts with area, type, and location.
Gang of Four Design Pattern Reference
All 23 GoF patterns grouped by Creational, Structural and Behavioural.
GoF Design Patterns Reference
All 23 Gang of Four patterns with intent and when-to-use, grouped into creational, structural and behavioral
Display Resolution Reference
All named display resolutions from QVGA to 16K
DNS Record Types Reference
Every DNS record type with RDATA format, TTL notes and use cases.
DNSSEC Record Types Reference
RRSIG, DNSKEY, DS, NSEC, NSEC3 record types with zone-signing role.
Docker Official Image Reference
Popular Docker Hub official images with tags and base OS.
Dockerfile Instructions Reference
All Dockerfile instructions with syntax, effect on layers and best-practice notes.
.env File Syntax Reference
.env variable syntax, quoting rules, comment handling and shell expansion notes.
Daylight Saving Time by Country Reference
Which countries observe DST and when they switch
E Number Additive Reference
E100–E1520 food additives with names and categories
TC39 Decorators Reference
Stage 3 JavaScript class, method, accessor and field decorator syntax and hooks.
ECMAScript Versions Reference
ES5 through ES2025 feature list with what each edition introduced
Electrochemical Series Reference
Standard electrode potentials for redox reactions
Electromagnetic Spectrum Reference
All EM spectrum bands with wavelength, frequency, and photon energy
Element Atomic Data Reference
Detailed atomic properties for every chemical element
Engine Oil Viscosity Grade Reference
SAE 0W-20 through 20W-50 grades for cars and equipment.
POSIX errno Reference
Search errno constant names and numbers across Linux, macOS and BSD.
ESLint Rule Categories Reference
ESLint rule categories — possible-errors, best-practices, ES6 — with rule counts.
ETag & Conditional Request Reference
ETag, If-None-Match, If-Modified-Since headers with strong/weak comparison.
Ethernet Standard Reference
10BASE-T through 400GbE standards with speeds and cables
EU Member State Reference
All 27 EU member states with accession year and currency.
Unix Exit Codes Reference
Search Unix and Linux process exit codes with POSIX and bash meanings.
Feature Policy / Permissions Policy Reference
All Permissions-Policy features with default allowlist and iframe inheritance.
fetch() Options Reference
All fetch() RequestInit options with type, default and cache/CORS/credentials notes.
Fibonacci Sequence Reference
Fibonacci numbers F(1) through F(50) for quick lookup.
find Command Reference
All find predicates, tests and actions with types and logical operators.
US State Flag & Motto Reference
All 50 US state flags, mottoes, and admission dates
Food Allergen Reference
The 14 EU major food allergens with examples
FTP Reply Codes Reference
All FTP three-digit reply codes with category and description.
Fuel Octane Rating Reference
RON, MON and AKI octane ratings by fuel grade and country.
Enhanced Fujita Scale Reference
EF0 to EF5 tornado intensity with wind-speed ranges and damage indicators.
G20 Member Reference
G20 members with GDP, population, and key economic indicators.
GCP IAM Predefined Roles Reference
Common GCP predefined IAM roles by service with included permissions summary.
GDB Debugger Commands Reference
Core GDB commands — break, run, step, backtrace, watch — with syntax and TUI notes.
GDPR Data Subject Rights Reference
All 8 GDPR data subject rights with response timelines.
GDPR Lawful Bases Reference
All 6 GDPR Article 6 lawful bases for processing personal data.
Gemstone Properties Reference
Mohs hardness, refractive index, and SG for major gemstones
Geologic Time Scale Reference
Eons, eras, periods and epochs with start dates in millions of years.
GHS Hazard Pictogram Reference
All 9 GHS hazard pictograms with signal words and examples
Git Command Reference
Essential git commands with flags and short descriptions.
Git Config Options Reference
All git config keys organized by section with type and scope (system/global/local).
GitHub Actions Contexts Reference
All GitHub Actions expression contexts and properties with type and availability.
Glove Size Reference Chart
Find your glove size from hand circumference in S/M/L and numeric sizing
Go Built-in Functions Reference
All Go built-in functions with signature, type constraints and panic conditions.
Go fmt Verb Reference
All Go fmt verbs with accepted types and output examples.
grep Flags Reference
Every grep / egrep / fgrep flag with description and POSIX/GNU flavor note.
GSM / LTE Band Reference
All LTE and 5G NR frequency bands by region with duplex mode.
HAR to cURL Commands Converter
Convert HTTP Archive requests to copy-pasteable cURL commands.
HATEOAS Link Relations Reference
REST HATEOAS link relation names — self, next, edit, describedby — with semantics.
Helm Template Functions Reference
All built-in Helm / Sprig template functions with signature and example.
HS Code Chapter Reference
Find the right Harmonized System chapter for any product
HSTS Preload Requirements Reference
Strict-Transport-Security header requirements for preload list inclusion.
HTML Global Attributes Reference
All global HTML attributes with type, inherited flag and browser support.
HTML Elements Reference
Every HTML5 element with content model, allowed attributes and ARIA role.
HTML Entities Reference
Look up HTML named entities, numeric references and the characters they produce.
HTML Input Types Reference
Every HTML input type value with accepted attributes and mobile keyboard hints.
HTML <link> rel Values Reference
All HTML link rel values with valid link types, effect and browser support.
HTTP Alt-Svc & Upgrade Reference
Alt-Svc, Upgrade, HTTP2-Settings headers with protocol negotiation flow.
HTTP Cache Header Reference
Search Cache-Control, ETag, Expires and Vary directives with CDN behavior notes.
HTTP Digest Auth Parameters
HTTP Digest Authentication header parameters — realm, qop, nonce, nc, ha1.
HTTP Forwarded Header Reference
X-Forwarded-For, X-Forwarded-Proto, Forwarded header syntax with proxy chain notes.
HTTP Prefer Header Reference
RFC 7240 Prefer header preference tokens with server return and respond-async.
HTTP Priority Header Reference
HTTP Priority, Urgency and Incremental field values with fetch priority mapping.
Web Push Notification Headers Reference
TTL, Urgency, Topic headers for Web Push with VAPID Authorization format.
HTTP Range Request Reference
Range, Content-Range, Accept-Ranges headers with byte-range syntax and 206 flow.
HTTP/2 Server Push Reference
HTTP/2 PUSH_PROMISE frame mechanics with deprecation notes and 103 Early Hints
HTTP Status Code Reference & Security Implications
Look up any HTTP status code with security and caching implications explained
HTTP Structured Fields Reference
RFC 8941 structured header item, list and dictionary syntax with sf-* types.
HTTP/2 Frame Types Reference
All HTTP/2 frame type codes with flags, payload structure and stream context.
ICD-10 Chapter Reference
Browse all 22 ICD-10-CM chapters with code range and description
ICMP Type & Code Reference
Browse ICMP types and codes for ICMPv4 and ICMPv6 with descriptions.
Igneous Rock Classification Reference
Common igneous rocks with texture, composition and formation.
IMAP Response Codes Reference
IMAP tagged, untagged and response code tokens with RFC 3501 context.
IMDG / IMO Class to UN Class Cross-Reference
Cross-reference IMDG hazmat classes to UN dangerous goods classes.
IMF SDR Basket Reference
The 5 currencies in the IMF Special Drawing Right basket with weights
Incoterms 2020 Reference
All 11 Incoterms 2020 rules with obligations and risk transfer points
IndexedDB API Reference
IDBDatabase, IDBObjectStore, IDBIndex and IDBCursor methods with transaction modes.
Infant Mortality Rate by Country Reference
Deaths per 1,000 live births for all countries (UN data)
Inflation Rate by Country Reference
Latest CPI inflation rates for all countries
Insurance Term Reference
Core insurance terms — premium, deductible, co-pay, subrogation — with search.
International Postage Zone Reference
Royal Mail and USPS international zone groupings
Internet Penetration by Country Reference
Internet users and penetration rate for major countries.
IntersectionObserver Options Reference
root, rootMargin and threshold options with bounding-box and intersection-ratio notes.
iOS Info.plist Keys Reference
Important iOS Info.plist keys with value type, required flag and usage description.
iptables Targets Reference
All iptables/ip6tables target names with required modules and behavior.
Island Nations Reference
Sovereign island nations with area, population, and ocean
ISO 27000 Series Reference
Information security management standards (ISMS) at a glance.
Historic Currency Code Reference
ISO 4217 codes for currencies no longer in circulation
ISO 9000 Series Reference
Key ISO quality management standards and their scope
Java Exception Reference
Browse checked and unchecked Java exceptions with class hierarchy and causes.
JavaScript Operators Reference
Every JS operator with precedence, associativity, types and examples
JavaScript Promise API Reference
Promise methods, combinators and async/await patterns in one searchable table
Jest Matchers Reference
Every Jest expect() matcher with argument type and async variant.
jq Filter Reference
Every jq filter, operator and built-in function with description and examples
JavaScript Error Types Reference
Every built-in JS Error subtype with throw conditions and message patterns.
JavaScript Intl API Reference
Intl.DateTimeFormat, NumberFormat, PluralRules, Collator options reference
JavaScript Temporal API Reference
Temporal.PlainDate, ZonedDateTime, Duration and Calendar types with key methods
Key Derivation Function Reference
PBKDF2, bcrypt, scrypt, Argon2 KDFs with parameter guidance and security notes.
kubectl Cheatsheet
Search kubectl commands by verb and copy them in one click.