Intellibook API vs Non-Working Days API

Two free Calendar APIs compared on access, reliability and developer ratings, using data from our daily health checks.

The verdict

Choose Intellibook API if you want faster responses.
Choose Non-Working Days API if its data fits your use case better; on access and reliability it's level with Intellibook API.

	Intellibook API	Non-Working Days API
What it does	Appointment booking and availability API for salons and clinics.	Simple REST API for checking working, non-working or short days for Russia, CIS, USA and other.
Provider	intellibookai developer resources	isDayOff()
API key	Not needed	Not needed
HTTPS	Yes	Yes
CORS (browser calls)	Yes	Yes
Status today	Online · 1280 ms	Online · 2770 ms
Uptime (30 days)	Up	Up
Developer rating	Not rated yet	Not rated yet
Price	Free / free tier	Free / free tier

Appointment booking and availability API for salons and clinics.

Official intellibookai developer resources and REST API documentation by Intellibook AI.

Strengths

Simple REST API for checking working, non-working or short days for Russia, CIS, USA and other.

API производственного календаря

Strengths

Prototyping or a tutorial? Pick the one that needs no API key (both qualify).
Calling from a web page? You need CORS. Otherwise route requests through your own server or a serverless function.
Going to production? Favour HTTPS, a strong uptime record and a provider with clear rate limits and terms. Check each API's docs before you commit.
Still unsure? Both are free to try: send one request to each and compare the data you get back.

Neither needs an API key; you can call both straight away.