arcsecond.io
Multiple astronomy data sources
Science & Math
arXiv
Curated research-sharing platform: physics, mathematics, quantitative finance, and economics
CodeCogs
Render LaTeX equations in PNG, GIF, SVG, EMF, PDF, JSON, or download formats with styling options
CORE
Access the world's Open Access research papers
GBIF
Global Biodiversity Information Facility
iDigBio
Access millions of museum specimens from organizations around the world
inspirehep.net
High Energy Physics info. system
isEven (humor)
Check if a number is even
ISRO
ISRO Space Crafts Information
ITIS
Integrated Taxonomic Information System
Launch Library 2
Spaceflight launches and events database
Materials Platform for Data Science
Curated experimental data for materials science
Minor Planet Center
Asterank.com Information
NASA
NASA data, including imagery
NASA ADS
NASA Astrophysics Data System
Newton
Symbolic and Arithmetic Math Calculator
Noctua
REST API used to access NoctuaSky features
Numbers
Number of the day, random number, number facts and anything else you want to do with numbers
Open Notify
ISS astronauts, current location, etc
Open Science Framework
Repository and archive for study designs, research materials, data, manuscripts, etc
OpenAlex
Open catalog of scholarly works, authors, institutions, sources, and concepts
Purple Air
Real Time Air Quality Monitoring
SHARE
A free, open, dataset about research and scholarly activities
Sunrise and Sunset
Sunset and sunrise times for a given latitude and longitude
TLE
Satellite information
USGS Earthquake Hazards Program
Earthquakes data real-time
USGS Water Services
Water quality and level info for rivers and lakes
World Bank
World Data